PSA1190 | Overview of PAYE Settlement Agreements
From HM Revenue & Customs · PAYE Settlement Agreements
In the event of an employer making an overpayment of tax and /or Class 1B NICs theoverpayment must be repaid to the employer, follow PSA2110.
Under Regulation 116 where tax and/or Class 1B NICs is repaid to an employer after 19October following the year to which the PSA applies, interest will be paid from
19 October, or if paid later
the date the amount was paid
until the date the repayment is made.