Explain how do I check for duplicate invoice or sales receipt in QuickBooks?
Try given step to check for duplicate sales (invoice, sales receipt) numbers:
Select Transactions -> Sales
Click the number column to sort it
When the sales populate, it switch the numbers in ascending and descending order
Check for duplicates
There are some solution to avoid duplicate receipt number:
Use only register for one computer not one register for multiple computer.
Remember to reload shell Screen.
Close the register form computer.
Use one browser tab at a time.
More Infromation About sale receipt in Quickbooks