Q re parents

My parents are in their 80s . They have modest income ( pensions , and interest and rental income from joint assets ). Each of them is sent and fill in self assessment ( paper ) returns, generally have either small amounts of tax to pay or small amounts due back depending on interest rates . I posted their completed 23/24 returns last week, but found today they forgot to expense part of the managing fee on the rental. 1) For ease , they intend to add this portion to next year's property expenses as it is too complicated for them to re-print and re-post the self assessment- is this ok? 2) to avoid this in future can they sign up for online but have me or my brother ( not tax professionals ) help them navigate the online forms or fill them in on their behalf or is that only possible via a tax advisor? they are not computer literate.

Hi qreparents.
1. No, it needs to be included in the year that it relates to and they should send a letter to make the amendment.
2. For the filing of  tax returns it would only be a tax advisor as they need to be approved and have a code issued by HMRC.
Thank you.