Verifactu adaptation for bespoke management software
We adapt bespoke invoicing applications to the requirements of Spain's invoicing software regulation, working on the existing code rather than replacing the system already in service. Before anything is modified we document how the application currently behaves, so that by the end of the project it can be demonstrated that whatever was not meant to change still works as it did.
What the regulation requires
Royal Decree 1007/2023 requires invoicing software to generate a record for every invoice issued, chained to the preceding record by a hash that prevents subsequent alteration, and requires that record to be retained and made available to the Spanish tax authority. Software producers have been subject to the regulation since July 2025, while taxpayers themselves have until 2027, depending on which tax applies to them.
Compliance calendar
- July 2025
- The date from which producers and resellers of invoicing software became subject to the regulation.
- 1 January 2027
- Corporate income tax payers.
- 1 July 2027
- All remaining taxpayers, including those paying personal income tax.
These deadlines have been postponed several times, most recently by Royal Decree-Law 15/2025, so the applicable calendar is worth confirming with your tax adviser before planning the project.
The case of bespoke applications
Off-the-shelf software is brought into compliance by an update the vendor publishes. A bespoke application has no vendor to publish that update, so somebody has to open the code, find the point at which invoices are generated and modify it. In a good number of companies that code has not been touched in years and whoever wrote it is no longer available.
Replacing the application with a commercial product is not immediate either. Systems that have been in service for years accumulate numbering schemes, series, credit notes and special cases that are rarely documented, and that would have to be reproduced in the new system before the old one could be retired. For that reason, adapting what already works is often the more reasonable option.
Project phases
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Audit and recording of current behaviour
We record how the application actually behaves in service and build an inventory of the processes involved in issuing invoices. This phase is read-only, with no modifications to the system. It produces a scope report setting out the risks identified and a fixed price for the following phase.
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Adaptation
We implement the changes needed to meet the recording, chaining and retention requirements. Each modification is compared against the behaviour recorded in the previous phase, so that expected differences are accounted for and the rest of the application remains unchanged. Every modification is reviewed before delivery.
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Delivery and verification
The adapted application is delivered together with the verification report and the set of automated checks produced during the project, which remains in the client's repository and can be reused in later maintenance work.
Contracting options
The initial audit is contracted at a fixed price. The adaptation phase can also be contracted at a fixed price once the scope is known, or against a block of hours where it is preferable to proceed in stages. Any subsequent maintenance is arranged as a monthly fee with a service level agreement providing 8x5 cover.
Frequently asked questions
Can you work on an application you did not build?
Yes, and it is the usual case. The audit phase exists precisely so that the system is understood before any change is proposed, and its findings determine the scope and price of the adaptation.
Does invoicing have to stop during the adaptation?
No. The current system stays in service while the adaptation is developed, and changes are compared against its recorded behaviour before going into production.
What happens if we stop working with you?
The code and the automated checks produced during the project remain in your repository, so any other supplier can continue the work. A source code escrow arrangement with a third party can also be added if you prefer.
What penalties does the regulation carry?
The penalty regime provides for fines of up to €50,000 per financial year for using invoicing systems that do not meet the requirements, and up to €150,000 for software producers who market them. Assessing the amount applicable in any given case is a matter for your tax adviser.
Shall we talk?
Knowing what the application is built with and how it currently issues invoices is enough for us to say whether this is a contained adjustment or a larger project.
ZodMobile provides technical software development and adaptation services. Interpreting tax regulation and signing off on compliance are matters for the client's tax adviser.