If you create a new transaction with a date that relates to a previously filed period, it will create an exception in the open period. As you are viewing a VAT 100 report that report doesn't show exceptions, select taxes, select prepare/submit return to the right of the open period and this will show you an exception column.
Any new transactions added in for a date within a filed period will be included as exceptions in the current period. You will be able to see these by selecting prepare/submit return, as my colleague previously suggested.
Thanks for your reply.
I can see the transactions in the Exception report but I thought that they should also be carried through to the VAT 100 and VAT Detail report? The VAT 100 does not include any of the transactions which I have entered late in previous quarters, only the ones made in the most recent quarter? How do I actually reclaim late entered transactions from previous quarters?