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HMRC internal manual

National Insurance Manual

Class 1A National Insurance contributions: Refunding Class 1A NICs: Offsetting Class 1A NICs overpayments against unpaid Class 2 NICs

If the person liable to pay Class 1A NICs that are due for refund is self-employed, for example a partnership or sole trader, any outstanding Class 2 NICs underpayments should be identified and offset against the Class 1A NICs refund.