Registering as a non tAxpayer

Registering as a non-taxpayer is not new. It is a reasonable thing for many pensioners to do, particularly married women with a limited contribution record in their own name. It is really up to the bank as to whether you need to re-register, but I don't think any of them require you to do so.

You must de-register if you income makes the interest taxable, or submit a tax return.

You can also have the tax taken and then request a refund from HMRC, although they would probably prefer not to handle large numbers of such claims from people with otherwise simple tax affairs. If you are likely to over some years and under others, it is probably better not to register, as doing the refund form should be easier than a tax return; for a start, you don't have to get it in by the end of January.