The tax code is a specific identifier used by HM Revenue and Customs (HMRC) in the UK for taxpayers residing in Wales who have a slightly adjusted personal allowance.
This is where the C1251L code differs from the standard. The prefix "C" is a specific geographic and administrative indicator. It stands for . c1251l tax code
You will likely see C1251L on your payslip if one of the following three scenarios describes your situation: The tax code is a specific identifier used
Then resubmit with the corrected code and country. Example: c1251l tax code