What do you get back from the Tax man after you file a self tax assesment form?

They will usually send you a new Tax Code ..

Sometimes you might get a cheque (if you paid too much Tax) .. sometimes, if you underpaid & owe more than about £2,000) a demand that you pay up in part installments ...

One other thing they might send is a re-calculation of your tax if you have made an error or if you have not included all income etc.

A tax Bill, telling how much to pay and how much trouble you'll be in if you don't pay it in time.