Can I replace a receipt that has been uploaded?
This article explains that yes, an uploaded receipt can be replaced in ExpensePlus.
Purchases with a receipt yet to be checked
If the receipt is yet to be checked, the user who submitted it, or a Finance User, can simply go to the purchase, select 'I'd like to replace this receipt' and attach a new file. This file will override the original file that was uploaded/emailed.
Purchases with a receipt that has been checked
If you accepted or approved a receipt by mistake and it has already been checked, only a user with the role of Finance Team will be able to replace the uploaded receipt.
A user with the role of Finance Team can simply go to the purchase, select 'I'd like to replace this receipt' and attach a new file.

Purchases with receipts that are replaced will go back through the receipt check process.
The purchase won't require approval again if it was previously approved by the budget holder, unless the budget details have been changed too.
For security, when replacing a receipt, new receipts can't be emailed in directly. They can only be replaced by being uploaded or photographed. This is to prevent receipts from being overridden by accident.
To help you better understand the Receipts module as a whole, please visit the module overview page here.