PAYE11085 | Coding: codes: how they are used and calculated: types of code
From HM Revenue & Customs · PAYE Manual
Most tax codes are made up of a number followed by a letter, for example 747L. We call these suffix codes.
There are other tax codes for special cases.
The main ones are
Prefix D code - used to charge tax at the higher rate and the additional rate
Prefix K code - for cases where coding deductions exceed allowances
Prefix S code – indicates the individual is a Scottish resident and tax is deducted at the Scottish income tax rates
Prefix C code – indicates the individual is a Welsh resident and tax is deducted at the Welsh income tax rates
Code BR - used to tell the employer to charge all payments to basic rate tax only
Code NT - used to tell the employer not to tax any payments