JMHZ from April 2026: Ensuring Payroll Software Compliance and Filing Accuracy

Ing. Veronika Sečková
Ing. Veronika Sečková
4.5.2026 | ARROWS law firm

As of 1 April 2026, the Unified Monthly Employer Report (JMHZ) has been launched in full operation. While the reform simplifies communication with public authorities, it also exposes issues with the readiness of payroll software. Incorrect reports may lead to penalties and complications with the Czech Social Security Administration (ČSSZ). This article explains how to communicate effectively with software vendors and ensure smooth submission of JMHZ.

The photo shows a lawyer addressing the issue of the unified monthly employer reporting obligation.

Key takeaways

  • The new system requires specific technical formats. JMHZ is submitted exclusively in  – the old paper-based or .xlsx approach is not possible, and your software must handle it flawlessly.
  • Data inconsistencies mean penalties, not just warnings. ČSSZ validates data in real time, and if the filing contains errors in mandatory fields, incorrect identifiers, or fields completed in a prohibited way, you may face a request for corrections, penalties, or blocked transactions.
  • The software provider is not legally bound to the quality of the export – you are. Statutory responsibility for the accuracy of the filing lies with the employer, not the software vendor. That is why you must be clear about what you require from them and how you will protect yourself in the event of a failure.
  • Preparation should already have been completed – you are now in live operation. The period from  is critical for verifying compatibility and submitting the first filings. If problems arise in May, it is often too late.

What JMHZ means for your company and payroll software

The Unified Monthly Report is not just another form invented by public authorities. It is a fundamental change in how a company communicates with public administration in the Czech Republic and how it manages its employees’ data.

Until the beginning of April 2026, your company likely submitted dozens of separate reports to various institutions – for example, pension insurance record sheets to ČSSZ (the Czech Social Security Administration), income data to the Financial Administration, social insurance reports, information on employees with disabilities to the Labour Office, and many others. Each report had a different form, a different format, different deadlines, and the same information was often repeated across datasets.

From April 2026, everything is centralised into a single electronic report, submitted monthly by the 20th day of the following month.

The report has three basic parts: a summary section with key company details and financial data, an insurance section with social and health insurance contributions, and an individualised section with information on each employee separately – start of employment, termination, sick leave, parental leave, and similar events.

This system means that your payroll software must not only calculate wages and withhold tax, but also export data in a precisely defined XML format so that the ČSSZ ePortal can accept and process it.

This is where the first critical point arises: many payroll software solutions used by companies were not originally prepared for JMHZ. Some are older systems, commercial solutions from small vendors, or bespoke in-house solutions – all of these systems need an upgrade, adaptation, or an entirely new module.

If your software is not ready, you essentially have several options: invest in modernising it, buy a new one, or temporarily export data manually and edit it in a spreadsheet editor. None of these options is ideal, which is precisely why more issues are being addressed in these weeks than employers expected.

What technical and data requirements JMHZ imposes on payroll software

If you feel that your current software should be compatible with JMHZ, the first step is to find out what that actually means. JMHZ is not a simple table export – it is a structured data format with precise rules based on regulations and methodological guidance issued by the Czech public administration. The software that generates the report must meet a wide range of technical and content requirements.

Most importantly, the report is submitted exclusively in XML format via the “Submission by uploading data from an accounting system” service on the ČSSZ ePortal. This means your software must have a function that allows you to export data into XML files, which you then upload to the ePortal.

Old methods, such as printing to PDF and manually completing a web form or inserting a table into Excel, do not work here. The ePortal does not accept these formats and the report will not be filed.

The second critical layer is the structure and content of the data. JMHZ must include a number of mandatory items with precisely defined formats and ranges.

This includes, for example, the employee identifier, their birth number (rodné číslo) or company ID number (IČ), the month for which the report is filed, the amount of income, withheld taxes, insurance contributions, applied tax credits, results of the annual settlement of advance payments, and similar items.

If the software exports data that contains an error in any of these items – for example, an incorrect date format, a prohibited character, or a missing mandatory value – the ePortal will reject the report and return a list of errors.

The third layer is the link to the employee register. Every employee included in the report must be registered in the ČSSZ system and have their basic details correctly completed.

If the software exports data for an employee who is not in the register or whose identifier is missing, the report will not be processed. This means the software must have access to data from the employee register and must be able to communicate with the ČSSZ ePortal or at least verify that the employee identifiers in the report are valid.

The fourth layer is managing multiple adjustments and corrections during the month. In real practice, it happens that during the month you discover that you calculated someone’s wage incorrectly, that an employee went on sick leave, or that insurance rates changed.

The software must allow you to make corrections and submit updated reports without compromising the integrity of the data in the system.

Typical data errors and their impact on filings

Looking at real filings that began arriving at ČSSZ from 1 April 2026, the most common issues are specific errors that lead to rejection or to a request from ČSSZ to correct the filing. It is important to understand what these are so that your software and your communication with the provider are directed the right way.

The most common error is missing mandatory fields. The report contains dozens of fields, many of which are mandatory – they must always be completed.

These include the employee identifier, their birth number (rodné číslo) or company ID number (IČ), the month for which the report is filed, the amount of income, the amount of insurance contributions, and many others. If any of these fields is left blank, the ePortal will reject the report and return an error message.

The software must therefore have built-in validation to check that all mandatory fields are completed before the report is exported at all.

The second group of errors involves prohibited or incorrectly completed items. The report also contains certain fields that should be completed only in specific cases or that have fixed, predefined values.

When software fills in something that should not be there at all, or when it fills in a value that is not on the list of permitted values (a code list), the submission will be rejected.

An example is a field relating to incapacity for work (sick leave) – if the software enters a value that is not defined in the Czech Social Security Administration (ČSSZ) system, the submission will contain an error.

The third group consists of incorrect combinations of identifiers. Each submission must contain the correct combinations of the company’s registration number (IČ) and its identifier in the ČSSZ system (employment ID), or the identifiers of payroll offices, as applicable.

If the software exports a submission with an IČ that does not match the employment ID or the payroll office registration, the submission will be processed incorrectly or not accepted at all.

The fourth group consists of formatting errors and character encoding. The XML format requires precise encoding and the use of permitted characters. If the software exports data that contain special characters (Czech diacritics) and they are not encoded correctly, the XML becomes invalid and the ePortal will not accept it.

If any of these errors occurs, ČSSZ will usually notify you first and give you time to correct it.

However, if the errors persist or there are too many of them, sanctions may follow – ČSSZ may impose a fine, may deny the effectiveness of the submission (which means your insurance contributions will not be recognised), or may prevent you from making further filings. In extreme cases, the matter may even escalate to administrative proceedings or penalties.

Most common questions on JMHZ technology and formats

1. Do we have to buy completely new payroll software for it to be compatible with JMHZ?. 
Not necessarily. Many existing systems, especially larger and newer ones, already have, or will soon have, a JMHZ module. First, ask your vendor whether they have an update you can apply. If they do, it will usually be cheaper and easier than buying a new system. If your vendor has no JMHZ plan, or the update price is disproportionately high, then you may consider purchasing new software.

2. Who is responsible if the software exports incorrect submissions?
The statutory responsibility lies with the employer – i.e., your company. If the submission contains errors and ČSSZ points them out or imposes a fine, you cannot excuse yourself by saying “the software did it”. If the error is caused by a software failure (for example, it systematically exports invalid XML), then you have the right to seek compensation from the vendor based on the purchase agreement and liability for defects. But only after you have experienced the issue yourself. That is why it is important to have a clear contract with the vendor and clear compatibility tests before going live.

3. What happens if, in May 2026, we find out that our software cannot export to JMHZ?
Then you have an urgent problem. You will still be required to file by 20 May for the month of April. If the software is not ready, you will have to export the data from something else (for example, your employee records or accounting), manually adjust it in an XML editor or spreadsheet, validate the format, and only then upload it to the ePortal. This is highly error-prone. The best strategy is to verify the status of your software today (i.e., no later than the end of April), purchase and deploy a new one if necessary, and test it several times with March and April data so that everything is ready in May.

Key points when communicating with your payroll software vendor

If you already have payroll software and need to communicate with its vendor about JMHZ readiness, it is important to know what to ask and how to ensure you receive precise answers. Many vendors are not used to providing the kind of declarative and legally binding answers you now need.

A clear plan and readiness timeline

The first step is to ask the vendor what their plan for JMHZ is and when the system will be ready. They should give you a specific date by which the functionality will be available. Ideally, this will be before May so you have time for testing.
If the vendor answers vaguely (“it will be soon”, “we’re on it”, “we’re discussing it”), that is a warning sign. Ask them to confirm in writing. If you receive a specific deadline by email or in an updated price list, you have it documented and can rely on it later if it is not met.

A detailed description of functionality

The second step is to ask what exactly the software will do. They should be able to describe that it will export XML in the exact format defined by ČSSZ and that it will validate the data before export.

Also, that it will be able to generate submissions separately for multiple payroll offices (if you have them), handle corrections and updates to submissions, and support all data you are required to report (start date, termination, sick leave, taking leave, etc.).

Request detailed materials – ideally a manual or specification of what the software can and cannot do.

Testing and go-live conditions

The third step is to plan how you will test the functionality. You should agree with the vendor that during March and April 2026 it will be possible to test exports on the ČSSZ test server or in a sandbox.

Also, that you will be able to export fictitious or real submissions and verify that the ePortal accepts them without errors. Many vendors offer a trial period – make use of it.

If the software fails during testing, that is the time to fine-tune it, not to panic during live operation in May.

Support and SLA

The fourth point is to make sure the vendor will provide support during the critical phase. Ideally, you should have a technical support contact who will be available during April and May, and a reasonably short response time (for example, within one business day).
If the vendor is a small company or a freelancer, it is especially important to ensure they are available. If they tell you they are only available via the web, or that they only respond on Fridays, that is not a good sign.

Update obligations and additional features

The fifth point is to clarify what happens if the public administration issues further guidance or changes the format. The Ministry of Labour and Social Affairs (MPSV) and ČSSZ have already issued methodological letters several times clarifying details on JMHZ. If the vendor releases new software or an update, they should provide it free of charge (or at least for a reasonable fee) if the changes are driven by changes in government regulation. Make sure this is agreed.

Liability and the option of a review

The sixth point is to make sure you have the option to get your money back or purchase services elsewhere if the software does not work. This is often addressed in the purchase agreement.
General law (Act No. 89/2012 Coll., the Civil Code) gives you certain rights in respect of product defects, but it is better to have this explicitly agreed in the purchase or licence agreement. The attorneys at ARROWS advokátní kancelář can help you review the contract with the vendor and ensure your rights are adequately protected – office@arws.cz.

Most common questions on negotiating with a vendor

1. Should we have the supplier sign a declaration that the software is ready for JMHZ?
Yes, that is a good step. If the software is already in live operation and the supplier claims it is ready, ask for a written declaration (an email is sufficient) stating that the software meets all JMHZ technical requirements and that the export will work correctly. If it later turns out this is not true, you will have evidence. If the supplier refuses to provide such a declaration, that is suspicious.

2. How much should modifications of old software for JMHZ cost?
It varies depending on the scope of the changes. For larger commercial systems, the price ranges from thousands to tens of thousands of Czech crowns, depending on how much the system needs to be changed. For smaller systems, it may be less. If the supplier offers you a price that does not seem right, feel free to check what others offer, or consult the attorneys at ARROWS, a Prague-based law firm, on whether the price is reasonable – office@arws.cz.

3. What happens if in December 2026 we find out that the software has an error in the JMHZ export and we have not noticed it for years?
That depends on how material the error is. If it is a systematic error (for example, the software systematically calculates insurance contributions incorrectly), you should have the right to claim damages from the supplier. If it is an isolated error that you should have found earlier, it is more complicated. The most important thing is to use the remaining months (April to September 2026) to check yourselves that the reports are correct. If you notice anything odd, notify the supplier and request a fix. This protects your rights.

Practical steps in communication with the supplier – checklist

To help you structure your communication with the supplier, here is a practical list of what you should manage during April 2026:

  • By the end of March 2026: You should have contacted your payroll software supplier and asked how prepared they are for JMHZ. Request specific information on the timeline, functionality, and testing options. Order an update if it is not included in the existing package, or arrange a demo of new software if you are considering a purchase.
  • Beginning of April 2026: If you have access to the ČSSZ test server, start testing the export. If it is not available, ask the supplier for a simulation—i.e., to generate a sample XML file that you can validate manually. Check that the export is correct and that ČSSZ accepts these reports.
  • Second half of April 2026: Submission of the first reports for the month of March. Carefully monitor what the ePortal returns to you. If the report is accepted without errors, that is a good sign. If error messages are returned, analyze them immediately and inform the supplier. Ask them to fix the software and test again.
  • End of April 2026: At the last minute, you should know whether the software is (or is not) ready for standard operation in May. If everything is fine, you can relax. If you are not sure, it is not too late to buy new software or arrange extraordinary support from your supplier.

Possible issues

How ARROWS helps (office@arws.cz)

The software does not work and the company cannot submit the report on time. There is a risk of a fine, the report being deemed ineffective, or a transaction being blocked.

We will provide you with legal protection against a fine—this is handled with ČSSZ, and if it is an objective failure of the IT system, it is possible to agree on a postponement. We also help companies draft a request for postponement or defend against a fine imposed by ČSSZ.

The report contains systematic data errors (incorrect insurance contributions, incorrect employee identifiers). This results in a notice from ČSSZ, a request for correction, and a potential fine.

We analyze whether it is a software error or an error in the input data. We handle communication with ČSSZ and, in line with their requirements, ensure the report is corrected and resubmitted. If the error is on the supplier’s side, we help you enforce a claim for damages.

The supplier fails to meet promises on time and the software is not ready. The company is left without a solution and is forced to handle the matter manually or in crisis mode.

We review the purchase agreement with the supplier and provide representation in negotiations with them. We can also file a court submission to enforce a contractual penalty or a refund, if justified. We also assist you with purchasing new software under tight time pressure.

The supplier leaves you without support in a critical phase and you have no one to ask. The company is left without technical assistance and risks further errors.

We help you find an alternative solution—whether that is hiring temporary IT support or purchasing a new software solution. If it constitutes a breach of a services agreement, it can also be addressed legally.

Communication with the supplier is not clear and the company is not sure what was agreed and what was not. This leads to misunderstandings, unexpected costs, and frustration.

We facilitate communication and prepare a written summary of all agreed terms. We help you formulate specific software requirements, which you then have documented and can rely on.

New records and employee identifiers – what it means for your software

In addition to the JMHZ export itself, the legislative change under Czech law also introduced new records and identifiers. This means your software must now also work with new data items and systems that it did not previously have to.

Specifically, each employee is now assigned a unique identifier in the ČSSZ system, which is used for all reports, registrations, and communication.

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Your software must therefore be able to work with this identifier—it may already have it loaded from the employee register, or it must be able to request or import it. If the software could not use this identifier in the past, it must now.

The second layer is that JMHZ introduces new categories of data that you previously did not have to report or reported differently.

This includes, for example, detailed information on an employee’s work and health capacity, information on withheld taxes, information on the use of social benefits, or information on corrections of contributions from previous years. The software must be able to manage and export all of this data into the report.

The third layer is that if you have multiple payroll offices, each of them submits reports separately. If your software previously worked with a central database of all employees, it must now be able to logically separate data by individual payroll offices and export it in separate files.

If your software does not have all these functions, or it has them but incorrectly, it will result in errors during the JMHZ export. That is precisely why it is so important to test it before going live.

Most common questions on records and identifiers

1. If we have an employee who worked for us last year and we now do not know their new identifier at the CSSA, what will happen?
You should find out this identifier. You can either retrieve it from the CSSA ePortal, where you can verify your employee records, or the information will be provided by the employee. If your software does not have the identifier filled in, the report will not be submitted correctly.
That is why it is important to carry out a check of all employees now (in March and April) and make sure you have all identifiers entered correctly. The CSSA insists on this – the identifier is mandatory.

2. What happens to the data of employees we employed from January to March 2026 if we are now sending the monthly report, but we did not have the information in the new system?
This is exactly why the months of January to March are in a transitional regime. Employers must submit the monthly reports for these months retroactively during April to June 2026, but only after they have completed all missing data in the employee register. Your software must be able to work with retroactive data – i.e., so that you can enter that employee X worked in February even if you only registered them in April.

3. If we have an employee from abroad or with a special status (self-employed, freelance/fee-based worker), how does the software handle them?
JMHZ has rules for various types of employment and for specific situations. The software must be able to distinguish between a standard employee and a person registered as self-employed, or someone working for the company under an agreement to perform work. If the software cannot handle this, it will run into problems. So ask your vendor about this functionality as well.

Timeline and time to prepare – what you do not manage in time will become a problem

From the launch of JMHZ on 1 April 2026, a very specific timeline applies, which companies must keep track of. If you misunderstand something or it does not go according to plan, a delay will arise that will then follow you for months.

The period from 1 March to 31 March 2026 was intended for employers to verify their employee records with the CSSA, add the new identifiers, and prepare for the new system.

This means that right now (in mid-April) you should be in the final phase of this preparation. If you did not make it, you should do so by the end of April, while it is not yet too late.

From 1 April 2026, employers are required to submit monthly reports. This means that the first report submitted in live operation is the report for March, submitted in April.

If you have your software ready and the report is error-free, that is fine. If there are errors, the CSSA will notify you and you will have time to correct them.

From 1 May 2026, employers must submit the report for April by 20 May (i.e., the “standard” deadline: from the 1st to the 20th day of the following month). This is already the standard regime – at this point it cannot be slowed down or explained away. If you do not submit the report, you face sanctions.

From 1 January to 31 March 2026, employers were not required to submit the monthly Single Monthly Employer Reports (JMHZ) within the standard deadlines. This is part of the transitional regime.

For the months of January to March 2026, employers must submit the monthly reports retroactively during April to June 2026 if they had employees in those months.

This means that in May the company will be submitting both the report for April (as standard) and, where applicable, also for one of the months January to March (if it has not yet submitted those reports retroactively), which is somewhat more complex.

The key point is: the preparation window is shortest right now. May and June are already live operation. If something is not ready, it will have impacts for years.

Security aspects and data protection

JMHZ works with sensitive personal data of employees – their birth numbers, income, tax data, health information (sick leave, maternity). When the software exports the report, it should ensure that this data is securely protected.

Specifically, this means that communication between your software and the CSSA ePortal should be encrypted (SSL/TLS). Furthermore, logging in to the ePortal should be protected by a strong password or two-factor authentication.

Exported XML files should not be archived in unsecured locations (for example, on unencrypted flash drives).

If your software cannot do this, or if you are not sure that the data is sufficiently protected, you should also address the security aspects with the vendor. This is not only an IT issue – it is also a legal issue.

Czech legislation (GDPR Regulation) provides that the provider, i.e., the operator of the software, must choose appropriate security measures.

If data were misused due to insufficient software security, the company that prepared the software could be liable. This is another argument for communicating clearly with the vendor and having clearly defined security requirements.

Customers, entrepreneurs, and HR-responsible persons – what you should know

If you work in an HR department, in a finance department, or are responsible for communication with vendors, you should now know the following:

In one word – preparation for JMHZ is happening now. It is not something you can leave for later.

The most important thing is to communicate with your payroll software vendor now (in April), find out how prepared they are, and factor in that you may need to buy new software, additional features, or external IT support.

In a second word – the company bears the responsibility, not the vendor. If the report contains errors, the CSSA will ask you to correct them and may impose a fine.

The software vendor does not share this responsibility (unless you explicitly agree it in the purchase agreement). Do not use this as an excuse – instead, spend the time to ensure the software works properly.

Third point – testing is free and essential. If you have access to the ČSSZ test servers, use them. If you do not, at least request sample exports and verify that they are correct. This testing can save you from a crisis.

Fourth point – in April 2026 there is no longer time for major changes. If you buy new software or make major changes now, you may still have a few weeks for testing. If you postpone it until May, it will be too late.

The attorneys at ARROWS advokátní kancelář can help you negotiate a supplier agreement, formulate software requirements, analyse risks, and, if things go wrong, also provide a legal solution to a dispute with the supplier – office@arws.cz.

Final summary

The Unified Monthly Employer Report is historically the biggest simplification of Czech administration – instead of dozens of forms, just one.

But that also means that this single form must be absolutely correct. If you make a mistake in one report, it is worse than when you previously had ten different forms and one contained an error.

Right now, in the second half of April 2026, you are in the middle of a critical period. Companies that are prepared are starting to submit their first reports and everything is running smoothly. Companies that are not prepared are experiencing chaos – their software cannot export, the ePortál returns errors, and they do not know what to do about it.

Your communication with your payroll software supplier is the most important factor at this moment.

If you are clear about what you want from them, if you have it agreed in the purchase agreement, if you have carried out testing and know the issues, then you have the prerequisites for success. If you have any uncertainty, now is the time to ask questions and address the matter with experts.

The attorneys at ARROWS advokátní kancelář deal with this topic in practice – helping companies align with software suppliers, analyse risks, provide legal defence in the event of failure, and, during the transitional phase, also communicate with ČSSZ. If you are not sure how to proceed, or if you already have problems with your software, contact us – office@arws.cz. Together, you can carry out an audit of your state of readiness and create a plan for how to safely get through the critical months ahead.

Most common questions about the Unified Monthly Report in practice

1. We already have old software that is 10 years out of date. Will we really not be able to use anything other than a new system that supports JMHZ?
In theory, you could continue using the old software for internal payroll administration, but to submit JMHZ you would have to export the data and manually edit it in an XML editor or a spreadsheet – which is highly prone to errors. We recommend purchasing at least a module or add-on for your software that will export in the JMHZ format, or purchasing new software.

2. If we submit a report with errors and ČSSZ points them out, how much time will we have to correct it?
The deadline for correction is not strictly defined by legislation – it depends on what type of notice ČSSZ sends you. Usually you have several days to respond. However, if it happens repeatedly, ČSSZ may no longer be patient and may impose a fine. That is why the most important thing is for the reports to be correct from the very beginning.

3. How much should new payroll software cost if we have to buy it?
The price varies greatly depending on the size of the company and the software’s functionality. Smaller companies with a simple agenda can buy software even for CZK 5,000–15,000 in annual subscription fees. Larger companies with more complex agendas may pay tens of thousands of Czech crowns per year. Some large enterprises develop software themselves or buy it for hundreds of thousands to millions. Ask for a demo and reference customers.

4. What should the procedure be if our software supplier promised that it would be JMHZ-ready, but in April says that it is not?
You should review the purchase agreement and check whether the JMHZ commitment is explicitly stated in it. If it is, you are entitled to a refund, a contractual penalty, or withdrawal from the agreement. If it is not, it is more complicated – general law will give you certain rights for a defective product, but not all of them.

5. Do we have to reprogram everything now? Can’t we take it simply?
JMHZ is not something you can afford to ignore – it is a legal obligation under Czech legislation. A company that fails to submit the report by the deadline risks a fine from ČSSZ. A company that submits a report with errors risks corrections, further fines, and potentially a blocked transaction. It cannot be taken so simply. You must set a clear plan and go through it with your supplier.

6. Are these all shared problems, or is it only us who have a problem?
These are shared problems – since the beginning of April 2026, thousands of companies in the Czech Republic have been dealing with the same issues. Many of them have the same problems with their payroll software. That is normal in a transitional phase. But companies that prepared in advance are now getting through without major issues. Companies that left it to the last minute are now experiencing stress. If you are not ready yet, you must manage it by the end of April.

Disclaimer: The information contained in this article is of a general informational nature only and is intended for basic orientation in the matter based on the legal status as of 2026. Although we take maximum care to ensure accuracy, legal regulations and their interpretation evolve over time. We are ARROWS advokátní kancelář, an entity registered with the Czech Bar Association (our supervisory authority), and for maximum client safety we are insured for professional liability with a limit of CZK 400,000,000. To verify the current wording of regulations and their application to your specific situation, it is necessary to contact ARROWS advokátní kancelář directly (office@arws.cz). We accept no liability for any damages arising from the independent use of the information in this article without prior individual legal consultation.

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