Dear Community,

As a Hungarian SAP Sales Consultant, I initially found it quite challenging to understand and correctly identify which invoice correction path should be used among the various options available in SAP, as well as which of these options are actually applicable in practice.

In this role, it is not sufficient to be familiar only with the system functionalities; a solid understanding of the underlying legal framework is equally important. This is also one of the reasons I decided to write this blog – to share practical insights on Hungarian invoice correction processes that may be useful for other consultants and users working in similar environments.

• Legal background
• Online invoice registration (reporting obligation)
• The correct modification index is key
• Credit Memo process
• Debit Memo process
• Multiple correction process
• Summary

As mentioned earlier, having a solid understanding of the legal background is essential, as SAP’s localized solutions are designed to support only compliant processes that ensure lawful operation. For both consultants and end users, this also means that when something does not work as expected, it is often worth checking whether the requirement itself aligns with Hungarian legislation or established best practices.

The most important regulation regarding sales invoices in Hungary is the Hungarian VAT law (Act CXXVII of 2007 on Value Added Tax). This law defines what information must be included on an invoice, how different types of invoices should be issued, and under what circumstances an issued invoice may be corrected or cancelled.

Another key regulation, particularly relevant in the context of NAV Online Invoice reporting, is the Act CLI of 2017 on the Rules of Taxation. This law sets out the requirements related to invoice reporting and registration. As a result, compliance with the provisions of both laws is mandatory to ensure correct and lawful operation.

As already outlined, this blog focuses on the sales correction processes, with particular attention to the modification index and the proper handling of invoice corrections. A fundamental principle in Hungary is that issuing an invoice correction without referencing a prior invoice is not permitted. Every correctional invoice must therefore be linked to an original invoice, as they are only valid together. For this reason, the legislation treats them as documents treated as equivalent to an invoice.

Since July 2018, Hungarian taxpayers have been required to report invoice data to the Hungarian Tax Authority (NAV) in (near) real time. To support this legal requirement, SAP provide a localized solution which is the Online Invoice Registration within DRC.

This obligation applies to:

• Original invoices issued in B2B transactions (currently all invoices between VAT-registered businesses, regardless of the invoice amount)
• All correctional invoices, such as credit notes and debit notes, which are linked to previously reported invoices

The data must be submitted in the prescribed XML format and must accurately reflect the content of the issued document, including all references to the original invoice.

As mentioned earlier, in correctional processes the modification index is a key element of the submitted XML, as it defines the position of the correctional invoice within the invoice chain. Accordingly, the tax authority (NAV) will only accept the invoice if the modification index is unique and correctly assigned.

In practice, this means that the first correctional invoice in a flow should have a modification index of 1, while subsequent correctional invoices (if any) should follow in sequence (2, 3, 4, and so on).

The localized Online Invoice Registration within DRC can correctly support this logic only if each correctional invoice is properly linked to the original invoice within the chain. In such cases, the system is able to calculate the modification index automatically during XML generation.

Therefore, in order to ensure compliant and lawful operation, it is important that these documents are created and maintained correctly within the system from the very beginning.

A Credit Memo Request is raised when the original invoice amount needs to be reduced – for example, due to damaged goods or pricing error. This credit note can generally be of two types:

• Price reduction – In this case the quantity is positive, but the net unit price is negative, so the total will be negative
• Quantity reduction – In this case the quantity is negative, but the net unit price is positive, so the total will be negative

The system determines this based on the attributes of the documents included in the flow, which is why it is important to use the appropriate document types within the invoice chain, even in cases where custom document types or process flows are defined.

Hungarian VAT Law requirement: The issued credit note must include the reference to the original invoice number, the nature of the correction, as well as the difference in the tax base and VAT amount. For NAV reporting, this document must also contain the reference to the original invoice and the corresponding modification index.

In SAP, to ensure lawful operation, a credit memo request or return order should be created with reference to the original sales invoice, without item selection. This ensures the correct linkage to the original VAT-relevant document. Once the correction flow is completed, the resulting credit note will include the reference to the original invoice as well as the appropriate modification index.

The submission and XML generation are handled by the localized Online Invoice Registration within DRC. Therefore, it is essential that the correct invoice chain and invoice data are properly mapped throughout the correction process to ensure compliant and accurate reporting.

A Debit Memo Request is raised when the original invoice amount needs to be increased – for example, due to additional services.

Hungarian VAT Law requirement: The issued debit note (supplementary invoice) must include a reference to the original invoice number and clearly indicate the additional tax base and VAT amount. In addition, the related NAV submission must contain the correct modification index assigned to this correction within the sequence.

In SAP, to ensure lawful operation, a debit memo request should be created with reference to the original sales invoice, without item selection. This ensures the correct linkage to the original VAT-relevant document. After this step, the debit note can be processed through the standard procedure.

The submission and XML generation are handled by the localized Online Invoice Registration within DRC. Therefore, it is essential that the invoice chain and invoice data are correctly and consistently maintained throughout the correction process to ensure compliant reporting.

In certain business scenarios, more than one correction may be required for the same original invoice – for example, a price correction followed by a quantity adjustment, or separate errors being identified at different points in time.

As mentioned earlier, in Hungary these correctional documents are not valid on their own, as they are always linked to the original invoice. For this reason, it is not possible to simply cancel a correctional invoice. If a previously issued correction needs to be cancelled – for example, if a credit note was issued but the product was later found not to be defective – this must be handled by issuing an additional correctional invoice, rather than cancelling the existing one.

▎ Important: You can not cancel a correctional invoice. In this case, you have to create an additional correction to the original invoice.

Key rule: Each subsequent Credit Memo Request or Debit Memo Request – regardless of whether a previous correction has already been processed – must always reference the original billing document, not the previous correction document.

Example flow with modification index:

Why this matters legally:

The Hungarian tax authority (NAV) requires that each correctional document must reference the original invoice, as these correctional invoices are not valid on their own but only together with the original invoice.

In SAP, to ensure lawful operation, credit memo requests and debit memo requests should always be created with reference to the original sales invoice, without item selection. This ensures the correct linkage to the original VAT-relevant document. Once this is in place, the correction flow can be completed as described above.

The submission and XML generation are handled by the localized Online Invoice Registration within DRC. Therefore, it is essential that the invoice chain and invoice data are correctly and consistently maintained throughout the correction process to ensure accurate and compliant reporting.

In all cases, the original billing document number is the mandatory reference. The modification index must reflect the correct sequential position of the correction in the Online Invoice Registration within DRC— no exceptions under Hungarian VAT law.