How to do a compliance check: records: statutory records: non-specified records
Where a person is discharging their own tax obligations, more decisions about record-keeping are left to their discretion. This is because only that person knows their own circumstances or businesses. They are in the best place to know what will need to be included in a return or whether they will want to make a claim. Based on that knowledge a person can decide what sort of records they must keep.
There is more guidance on record-keeping (HMRC website) on the HMRC website.