Check the current highest invoice number
Check the current highest invoice number:
Go to the Sales Transactions Enquiry screen.
Set Type to IN (Invoice).
Sort by Header Ref.
Select Descending.
Click Search. The top result in Header Ref is the highest invoice number already used.
Correct the invoice number
Correct the invoice number:
Click System, then click Options, then click System Options, then click the Documents tab.
Click Edit.
Change the Sales Invoice number to a value greater than the current highest.
Click Save.