First, check the email we sent you to let you know your receipt has been rejected. In this email we let you know why your receipt has been rejected and what you can do to fix it.
If your receipt can be re-opened for submission you will see a blue button on your receipt page 're-open receipt for submission'. Click this button to re-open your receipt, to add any missing documents.
If you do not see any button to re-open your receipt for submission, let us know by email and we will check if we can help you further.