You cannot change the invoice numbering completely but you can set the prefix on your invoice numbers:
- Go to 'Your Profile' at the top right
- Select 'Company Settings'
- Scroll down to the 'Auto Numbering' section
- In the 'Select an Object' field, choose 'Invoice'
- In the 'Prefix' field, you can add your unique job
Alternatively, you can edit your invoice template and add a specific number to each of your customer's invoices by following the steps below:
After you've created an invoice, on the preview page (before you email it):
- Press 'Customise this Document'
- Scroll down to 'Invoice Settings'
- Select 'Header'
- Overwrite the word 'Invoice' with 'Invoice + your specific customer invoice number'
- Press 'Save'
Please note that it is the user's responsibility to ensure that all invoices and credit notes issued to customers are compliant with HMRC’s rules on the issuance of invoices and credit notes. For more information, and to familiarise yourself with the latest advice, please refer to the government’s website.