How do I change the numbering system for sales invoices

I'll ensure you can effectively manage and customize your sales invoice numbering system in QuickBooks Online (QBO), seamus. 

QuickBooks Online (QBO) generates invoice sequence numbers from 1001 by default, but you can always change the invoice number by your preference.

To enable custom transaction numbers in QBO, follow these steps:

1. Go to the Gear icon in the upper right corner. 
2. Select Accounts and Settings under Your Company.
3. On the left sidebar, click on Sales.
4. Turn on Custom Transaction Numbers.
5. Click Save, then select Done.

Once this feature is enabled, an Invoice no. field will appear on your sales forms, allowing you to enter any number or letter format you prefer.

Please note that once custom transaction numbers are enabled, QuickBooks will follow your custom numbering sequence for all invoices going forward.

Once done, check out this article for the complete instructions on receiving and processing payments: Record invoice payments in QuickBooks Online.

Tag my name in the comment below if you encounter difficulties managing your invoices in QuickBooks. I'm always available to provide ongoing support and ensure everything works.