Duplicate invoice numbers

Every invoice number must be unique within your organization. Alya Books allocates numbers from a series when you save, so duplicates only arise when a number is imported or typed by hand (possible only when Allow manual document numbers is on).

How numbers are allocated

1. The editor pre-fills the number from the series for the document kind (invoice, credit note, debit note) using the template in Settings → Outgoing invoices → Document Numbering (tokens {YYYY}, {YY}, {MM}, {DD}, {n}).
2. The number is fixed when you save. If the next number in the series already exists, the series skips ahead automatically.
3. By default the number field is read-only, so every invoice takes the next number in order. If Allow manual document numbers is switched on (Settings → Outgoing invoices → Numbers, terms and editing) and you type a number yourself, the counter moves to that number so later invoices continue after it.

When a number is already used

• Saving an invoice with a number that exists fails with a "Failed to create invoice" error naming the duplicate. Change the number or clear it so the series assigns the next one (only possible with manual numbers on; otherwise the next free number is taken automatically).
• CSV imports skip rows whose number already exists and list them in the import result.
• Through the API, a reused invoiceNumber returns a validation error; GET /invoices/verify-number checks a number before you use it.
• Incoming invoices with the same supplier TRN and number as an existing one are rejected as duplicates.

Good to know:

• A rejected invoice keeps its number. After you fix and resubmit it, the new attempt uses the same number; the previous attempt stays visible on the E-invoicing Submissions card.
• Duplicate in the invoice menu copies the content into a new draft with a new number; it never reuses the original number.
• Credit notes, debit notes and proformas have their own series and prefixes, so CN-0001 and INV-0001 do not conflict.
• Do not renumber issued invoices. They are locked, and the FTA has already received the number.
• If you need a gap-free sequence, keep Allow manual document numbers off and avoid deleting drafts that already received a number (or switch off Reserve invoice numbers for drafts).

Related:

• Create a tax invoice
• Recurring invoices