Remove Profit and Loss transactions to take notice of the period

A customer of mine has backdated transactions in Sage 200 prior to running the year end, they didn't want last years nominal updated but they wanted to update their Customer and Supplier balances. Backdating these transactions using 30/4/21 is fine, and it set the period to 1 - which they are happy about. On running the year end and remove profit and loss transactions, it has removed these transactions due to the date, even though they are affecting this new year. If the process could be updated so it ignores these transactions with a period of this year, it would be really helpful.