VeriFactu guide

VeriFactu guide: what the chained invoicing register is

If you run a shop, you've probably heard the term "VeriFactu". Here we use its exact technical name — a chained invoicing register with a fingerprint — because "VeriFactu" designates one of two specific modes within the regulation, and we prefer to be precise about what your system does today.

What it is

What is a chained invoicing register?

A chained invoicing register is software that logs every sale linked to the one before it through its own fingerprint, so no record can be altered or disappear without leaving a trace: tampering with an old sale breaks the match of every fingerprint that came after it.

Before this requirement, till software could delete or edit a sale that had already been charged without leaving any visible trace, which made it possible to hide income or run a second, parallel set of books. A chained register closes that door by design: every receipt, every void and every refund is logged one after another in the same chain, and each till or terminal keeps its own, independent of the rest.

The regulation

What does Royal Decree 1007/2023 introduce for invoicing systems?

Royal Decree 1007/2023 sets out the technical requirements invoicing software must meet: generating every record correlatively and chained to the one before it, preventing it from being altered or deleted once created, and keeping it legible, traceable and stored for as long as it needs to be checked.

The rule builds on an obligation designed to put an end to software that can hide sales or run two different sets of books for the same business: rather than trusting that nobody will misuse it, it requires the invoicing system itself to guarantee that integrity by design, from the moment each record is created. It is the rule many people sum up with the name "VeriFactu". Exactly how it applies to your own business is something worth checking with your tax adviser.

Fingerprint and chain

What are the fingerprint and the chain of an invoicing register?

The fingerprint is calculated from the contents of a record, such as a sale or a void. Every new record also includes the previous fingerprint; if an older record changes, its recalculated hash no longer matches the stored chain.

That fingerprint is calculated with a mathematical formula that combines the record's own data with the fingerprint of the record before it, producing a completely different result at the slightest change to either one. Each till or terminal keeps its own complete chain, with its own series of records: checking that a chain is intact is the same as checking that no sale on that till has been touched after it was issued.

The receipt QR code

What is the QR code on the receipt for?

The QR code printed on a receipt makes its identifying data accessible to a compatible reader. Numbering, fingerprint and chain continuity are validated separately when the register synchronises with the server.

When the receipt includes its QR code, a compatible reader can interpret the data it contains. That reading does not replace validation of the fiscal chain; check the thermal printer head periodically to keep the code legible.

Choosing a POS

What should a business look for when choosing a POS?

Before choosing a POS, check that the system produces a chained register with its own fingerprint, that it prints a QR code on every receipt, that each till keeps its own series, and that the provider can clearly explain how that chain actually works underneath.

Always ask the provider for a clear explanation of how it generates the fingerprint and chains records together, and check that you can recover your full history if you ever switch systems. No tool can decide on its own whether your specific business is in good standing: that call belongs to your tax adviser, working from your business's real details.

Frequently asked questions

What do businesses ask about the invoicing register?

What exactly is an invoicing register?

It is the entry a computer system makes for every sale, void or refund, with its essential data (amount, date, reference) and its own fingerprint linking it to the record before it. That link, repeated operation after operation, forms a business's complete chain.

What happens if someone tries to alter a sale that has already been recorded?

That record's fingerprint stops matching the one calculated at the time, and that mismatch carries through to every later record in the chain. The chain does not physically stop anyone touching a database, but it does make any later alteration plain to see.

Does a chained invoicing register need an internet connection to work?

No. Calculating a fingerprint and chaining it to the previous one is a local operation that does not depend on any remote server. A system can keep generating valid, chained records even while a shop has no internet connection at that moment.

Is a chained register the same thing as a backup?

No. A backup keeps a snapshot of the data in case it is lost, but it does not stop anyone editing the original before it gets copied. A chained register, by contrast, makes any later alteration plain to see through the link between fingerprints.

Should every till in a business keep its own series of records?

It is standard practice, and how it works in real systems: each till or terminal keeps its own series of records, chained together. If a business runs several tills, each one keeps its own complete chain, and checking one does not require checking the rest.

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