Revenue and Customs tax codes.

It took me at least 30 minutes on the phone to get through to ask why that I had applied a tax code to two sources of income, one at 22% and another at 40% when whey had already issued codes to provide allowances first against that incomes.

It appears that although you may have had coding notices issued to say you should pay less tax, due to a R&C computer glitch they never actually reached the payers that apply the codes.

Astonishing and I am due a big refund.  You might want to check yours.