There used to be relatively generous yearly allowances for savings (£1,000) dividends (£2,000) and CGT (£12,300) which meant most people would be exempt and not

There used to be relatively generous yearly allowances for savings (£1,000) dividends (£2,000) and CGT (£12,300) which meant most people would be exempt and not have to fill in a tax return. Saving interest is often paid gross but if you go over the savings allowance and don't fill in a tax return HMRC will just automatically take more tax from your payslip. There is also a £20,000/year ISA allowance which shields investment from tax so any holdings within an ISA can be ignored for tax purposes. However, the dividend and CGT allowances have been reduced recently as the government tries to find ways to raise more revenue without raising the headline tax rates, and the £20k ISA allowance hasn't been raised for years despite inflation. So as it stands, in the future a lot more people will have to start filling in tax returns.