Issuing compliant invoices when the internet is down

The router fails at 8:40pm on a Thursday. There are fourteen people in the queue. What are you allowed to do?

The short answer

If you issuesimplified tax invoices (retail and restaurant counter sales), you can keep trading —if your point of sale can sign invoices on the device. Simplified invoices are reported to ZATCA within 24 hours, not cleared before issuance, so the network is needed for the report, not for the invoice.

If you issuestandard tax invoices to businesses, those require clearance and clearance requires the authority. You cannot issue a cleared standard invoice offline.

Why on-device signing is the whole question

The cryptographic stamp on an invoice is produced with the device's production certificate. Two architectures exist:

Signing on the device. The certificate and private key live on the terminal. The stamp is computed locally, in milliseconds, with no network. The invoice is complete and valid the moment it prints.

Signing on a server. The terminal sends invoice data to the vendor's server, which signs and returns it. Fast and convenient — and completely dependent on connectivity. When the line drops, this architecture cannot produce a valid invoice at all.

This is not a marketing distinction. It determines whether your shop can trade during an outage. Ask which architecture your vendor uses, and then test it by unplugging the router; ouroffline comparison has the ten-minute protocol.

What must still be true offline

An offline invoice is not a lesser invoice. It must still carry:

• The full UBL 2.1 XML structure
• A correct UUID
• Theprevious invoice hash, continuing the chain from the last invoice this device issued
• A valid cryptographic stamp from the production certificate
• A complete Phase 2 QR code including hash, stamp and public key
• Correct VAT calculation per line

The hash chain deserves attention. Offline invoices continue the same chain. A system that starts a separate chain offline and tries to merge it later produces a break that is visible to the authority.

The 24-hour window

Simplified invoices must be reported within 24 hours of issuance. During an outage the clock is running. Practical consequences:

• A two-hour outage is a non-event; the invoices report when the line returns.
• An outage lasting into the next day needs attention. If connectivity is not back, get the invoices reported some other way — a mobile hotspot from a phone is usually enough, because reporting is a small amount of data.
• Your system should show you a count of unreported invoices, prominently. If you have to go looking for that number, the design is wrong.

Wameed keeps issuing for 24 hours offline and shows the pending-report count on the terminal and in the back office, retrying automatically as soon as the line returns.

The staff fallback procedure

Write this down, print it, and put it under the till. Rehearse it once.

1. Confirm it is the internet and not the power. If the terminal is on, keep going.
2. Keep selling normally. The system is designed for this. Do not switch to handwritten receipts if the terminal is issuing signed invoices.
3. Do not restart the terminal. A restart during an outage risks losing unsynced state on some systems.
4. Tell the manager, with the time it started.
5. Take card payments only if your payment terminal has its own connectivity — a separate mobile data path often keeps working.
6. When the line returns, confirm the pending count returns to zero and check the back office for rejections.
7. If the outage passes 12 hours, use a phone hotspot to let the terminal report.

What to do if your system cannot sign offline

Be honest about the risk and mitigate it deliberately:

• Get a backup connection — a 4G/5G router with automatic failover is inexpensive and solves most of this
• Know your manual procedure and make sure it complies: a handwritten note is not a tax invoice, and the sale still needs a compliant invoice issued afterwards
• Ask your vendor for a roadmap commitment in writing
• Price the risk: revenue per hour at peak × expected outage hours per year

For many shops the backup connection is the right answer and is cheaper than switching systems. For shops where the connection is chronically bad, changing to a system that signs locally is the structural fix.

What Wameed does

Sales, ZATCA signing and printing continue for 24 hours without a connection, on the native terminal appand in the browser cashier. The hash chain continues unbroken, reporting resumes automatically, and the pending count is visible everywhere. The one exception is the kitchen display, which needs the local server — we say so on theZATCA page.

Not tax or legal advice. Confirm your obligations with ZATCA or your tax adviser.