“There are much bigger fish for them to investigate”
Sadly, you are wrong katy. VERY wrong.
My wife underwent investigation last year for a discrepancy in Building society interest. A quite small amount. The IR knew the building society account and the amount. We had forgotten about this account as it was only open for a matter of 2 months as a place for the deposit on a property. They then insisted we explain every credit to our current account over the last year. This for a sum of no more than £50 in tax.
I repeat that Bulding societies report all significant interest payments to the IR. These are automatically compared to your tax return and all discrepancies are investigated. If you don’t fill in a tax return, or only pay tax at the lower rates, i suppose you are at less risk.
I’m just trying to be helpful. Be careful if you do this.