Do you get Tax Returns? If so, don't worry about it and it'll all come out in the wash. If not, what you should do next depends on whether or not your bank attempts to correct the mistake. If they don't, I'd suggest you write exactly once to the Tax Office who deal with you, quoting your NI number, explaining the situation as briefly as possible (pref. in words of one or fewer syllables) and showing the amount of tax not paid. Make sure it's clear which tax year(s) are affected. If the tax office want to do anything about it, they'll then change your tax code or send you a Return or somesuch. You risk that, if your bank then later decides after all that it is going to claw the tax off you, then it'll get even more fiddly...