Invoice numbers exist so you and the customer can reference a specific bill. The system you use matters less than that you have one and stick to it. But some systems are noticeably better than others.
The three main systems. Sequential (1001, 1002, 1003) is the simplest and what most software uses by default. Dated (2026-001, 2026-002) makes it easy to see at a glance what year an invoice belongs to. Prefixed by customer (ACME-001, ACME-002) makes each customer's invoice history e
Why the first number matters. Starting at 1 tells your first customer they're your first customer. Starting at 1001 or 5000 doesn't. It's a small psychological signal but a real one — especially if you're brand new and pitching to bigger clients.
Formats that hold up over time. Good formats scale as your business grows:
What to avoid. A few patterns that cause problems:
Voiding vs deleting. If you create an invoice by mistake, void it (set the total to zero, keep the number in the sequence) rather than delete. This preserves the audit trail and prevents gaps. Glo Invoice handles this automatically — voided invoices stay in your history with a cle
Frequently asked questions
Is there a legal format for invoice numbers?
Not in the US. Some countries (particularly in the EU) require sequential numbering by law. In the US, any consistent system is fine as long as numbers aren't duplicated.
Can I have separate sequences for different services?
Yes, using prefixes. 'RES-1001' for residential, 'COM-1001' for commercial. Just make sure each sequence is unique on its own.
What happens if I skip a number?
Nothing legally, but auditors and CPAs get curious. Better to void unused numbers than skip them.
