To recover the bill number previously deleted, please follow the steps below:
Go to Setup, General Setup, Last Used Nos.
Look for Supplier Invoice, Deliver Order, Invoice, Debit Note, Credit Note, Cash or any bill, and untick the check box for running number.
Create the bill and manually input the missing number.
Once the bill is completed, go back to Setup, General Setup, Last Used Nos.
Tick the check box for running number again to continue with the running number sequence.
Example: If the last used number is 00000001, when you add a new transaction, it will prompt you to manually input the reference number.