SemiAuto Invoicing Pro features a sequential numbering engine that prevents duplicate or missing invoice numbers:

• Go to WooCommerce → Settings → PDF Smart Receipts → Invoices.
• Configure your Invoice Prefix (e.g. INV-2026-) and Next Number (e.g. 1001).
• Under Numbering Moment, choose whether numbers are locked upon order payment or when the email is sent to the customer.

Note: Draft invoices do not consume sequential numbers, ensuring zero gaps in your accounting ledger.