Switching invoicing software mid-year: numbering, history and a scare-free move

Switching invoicing software mid-year: numbering, history and a scare-free move

"I'd better wait until January" is the sentence that keeps thousands of businesses one more year on software they hate (or on a spreadsheet that is no longer legal). The truth: you can migrate any day of the year if three things are solved properly — numbering, history and the cut-off. None of them is hard.

Numbering: continue, don't restart

The legal rule is sequential numbering per series, not "start at 1 in January". Two correct paths:

• Continue the existing series: if you're at F-2026-0141, the new system starts at F-2026-0142. In InvoSeal you set the initial number when creating the series, and sequence stays intact.
• Open a new series from the cut-off: say, series "B-2026" from 1 November. Perfectly valid: each series is sequential in itself. The cleanest option when the old program's history is chaotic.

The only forbidden things: reusing numbers already issued, or leaving gaps within one series. That's why the switch needs an exact agreed date: last invoice there, first one here, and nothing issued astride both systems.

History: retaining is not migrating

Invoices from the last 4 years (6 for commercial-law purposes) must be kept and producible — but they don't have to live in the new system. Options by effort:

1. A full export from the old program (PDFs + record books), archived in your hands. Legally sufficient. Do it BEFORE cancelling the old subscription: "read-only access forever" has a habit of disappearing. 2. Load the master data: customers (with VIES-validated VAT numbers), products and price lists — fifteen minutes with the importer and you invoice normally from day one. 3. Import the invoice history too, as a searchable archive, if having everything in one place pays off for you.

The perfect cut-off, in five steps

1. Pick the date (a Monday or the 1st helps the mind, but any day works). 2. Export everything from the old system: PDFs, books, customers, products. 3. Set up InvoSeal: tax data, logo, series (with initial numbers), customers, products, recurring templates. 4. Issue an internal test invoice and verify series, number, QR and the bilingual PDF. 5. Disable issuing in the old system (not viewing) on the cut-off date.

The two avoidable scares

• The duplicated recurring invoice: if the old program had automatic invoices, switch them off explicitly — the classic November with two retainer invoices.
• The 347/303 of the transition year: your books will come from two systems. The full export from step 2 plus InvoSeal's books from the cut-off give your advisor the whole year with no holes.

Migrating from a specific program and want us to look at your case (odd series, pending corrective invoices, inherited numbering)? A Support ticket with two screenshots and you'll get the cut-over plan back, done.