Informing HMRC of NEST and SIPP contributions

What's the simplest way to inform HMRC of NEST and SIPP contributions made in the 23/24 tax year? I know this can't be done by email. Could this be done by phone or webchat? Could I upload the relevant documents securely to HMRC? When HMRC add basic rate tax relief to a SIPP or to a NEST pot, why don't they record it against the personal tax account of the taxpayer who made the pension contribution?

Hi NedFlanders,
If payments are less then £10,000 you can contact the Self Assessment helpine to have your tax record updated.
IF you need to write in with evidence please send to:
HMRC PAYE & Self Assessment BX9 1AS
Thank you.