I have an LX tax code. As it stands at the moment I have overpaid for the year. Will this all be corrected on my final payslip of the tax year?
You would need to seek guidance from hmrc or do the manual calcs , week 1 codings (X) dont adjust for earlier unders/overs so normally the answer would be know - but hmrc now often do a calc that should get things back on track by adjusting your code for the known difference and using different code on w1/m1 basis for the rest of the year, whether this cunning plan of theirs will work is anyones guess.
For manual calcs its easy if your salary will be consistent - as long as the w1/m1 code is applied the tax should be the same each month - normally any extra/less is taxed at the normal marginal rate - so add up the rest of the tax years amounts on this basis and see if the year end calcs work out as they should do.