Digital Signatures on Accounting Documents - Why the Law Requires Them
A digital fiscal document (a tax invoice, transaction invoice, or receipt) produced by a computerized system must, under Israeli law, be digitally signed to be considered valid. It isn’t enough for it to just “look like” an invoice PDF.
What separates a regular PDF from a digital signature
A PDF generated from a Word or Excel template can be edited again with no trace: you can open it, change an amount, and save it again without anyone knowing. A digital signature ties the exact content of the document to a cryptographic signature at the moment it’s issued - any change to the content, even the smallest one, will cause the signature to fail verification. That’s what makes the document trustworthy, both to the Israel Tax Authority and to the customer who receives it.
When the document gets signed
Signing happens at the moment of issuing, not when the draft is created and not when it’s printed. Once a document is signed, it’s locked: it can’t be edited, deleted, or changed in any way. Fixing a mistake on a signed document can only be done through a credit note (see the separate guide).
What actually gets stored
Along with the signature, a permanent snapshot of the document is also stored, exactly as it was when signed - including the business’s details, the customer’s details, the line items, and the amounts as they were at that moment. Even if the business’s settings change later (an address or logo, for example), older documents keep showing the details that were correct on the day they were issued, not the current ones.
Verifying against the customer
A digitally signed document usually includes a QR code or a verification link, letting anyone who receives it confirm that it’s genuinely identical to what was originally issued and hasn’t been altered along the way.
What happens without a proper digital signature
Issuing fiscal documents in a format that doesn’t meet the signature requirements exposes the business to having those documents rejected in an audit, even if the amounts on them are completely correct - a document’s legal validity depends on meeting the signature requirement, not just on its content.
How Slate signs digitally
Every document issued on Slate (an invoice, receipt, or credit note) is automatically digitally signed at the moment of issuing, and stored as a permanent, unchangeable snapshot. There’s no separate setting to turn this on or opt out of it.