Tax Relief on SIPP contribution of over £10K and Taxable interest over £1K

If a 40% taxpayer has paid £25K gross into a SIPP this year and has received about £3K of taxable interest can they register for self assessment in order to: A) Get the extra relief on the SIPP contribution and B) Declare the taxable interest The extra payments to the SIPP and taxable interest may be ongoing but different amounts each year. It seems simpler to declare these amounts each year on a tax return (to correct each tax year after it ends) rather than have the tax code adjusted. Wouldn't tac coded adjustments assume the same amounts of SIPP contributions and interest received each year? I notice that this does not seem to be a criteria for self assessment in the absence of self employment or rental income. Can you elect to do self assessment voluntarily?

Hi Bally53,
You can read more and register here:
Register for Self Assessment if you are not self-employed
Thank you. 

I read this guidance before asking my question. I have looked at form SA1 but my reason does not fit the criteria. I paid over £10,000 as a one off contribution into a SIPP at the end of the 23/24 tax year. I am an employed 40% taxpayer. The pension scheme has received the 20% basic tax relief. I tried to register for self assessment to tell HMRC about this £10K contribution and also some untaxed interest but with no response. I don't know if this is because you are behind with registering people or if you don't want me to do self assessment for this reason. Therefore I wrote to HMRC on 25/8/24 with evidence. There is a facility to ask how long it will take you to reply but the reasons in the form do not include extra SIPP contributions. https://www.gov.uk/guidance/check-when-you-can-expect-a-reply-from-hmrc The relevant tax year has ended and therefore I will be due a refund of some tax already paid. When can I expect HMRC to calculate the refund I am due?