izzaig G

Firstly, I received a letter giving me a new tax code today , but in the letter, it stated that I was informed of the tax I owe from earlier year but I have never received that letter . Secondly, I already received a letter in December 2024 about untaxed interest from 2023 to 2024 and I have paid the amount HMRC asked for. Now I am confused why I receive the letter today saying I have untaxed interest less adjustment for tax I owe for earlier year, which I have already paid. This is the reason now I have a new tax code. My question is, how does HMRC estimate the savings interest ? There is no break down of the calculation and I believe the calculation is over stated and the tax code is going to 'over calculate' and end up reducing my take home pay. Thank you.