I know this subject has been hammered to death recently and I apologise if I've missed something whilst on holiday.
A subby client who normally receives tax refunds is facing a massive tax bill next January due to SEISS grants claimed, pushing a substantial part of his income into the 40% bracket; obviously without CIS tax suffered. Many people have suggested changing the AP and claiming overlap relief. Circumstances are a 30/04/2020 year end plus SEISS ( which actually supported his considerable lost income in year ended 30/04/2021 ).
I can only see that his AP could be extended which in fact increases his 2020-21 income and therefore increase his tax bill. Overlap relief restricted to 6/11ths of brought forward overlap relief, which doesn't cover the increased income.
This is my first change of AP in 35 years of practice, so am I missing something ?