NIM38501 | Refunds: Class 2, 3 & 4 NICs: General
From HM Revenue & Customs · National Insurance Manual
Regulations 51-52, 56-57, 101-102 & 109-110, Social Security (Contributions) Regulations 2001 (SI 2001 No. 1004)
A contributor is entitled to a refund if:
contributions are paid above the annual maximum (see NIM38505); or
contributions are wrongly paid due to an error which occurred at the time of payment; or
Class 3 contributions are paid which cannot count for or increase benefit entitlement (such Class 3 contributions are precluded in law - see NIM25005 (contents))