Please could you confirm the correct taxation principle in the following scenario.
A member is paid on a Month 1 basis.
We are in tax month 1. He is paid £300 under 850L (M1) tax code and taxed appropriately.
His tax code then changes to 650L.
He is then paid a further £200 (still in tax month 1). Should just this additional £200 be taxed under 650L or should the whole £500 received in month 1 be taxed under 650L (essentially reassessing the tax on the first £300).
Also please could you have a look at my additional comment on K0 tax codes in another post.