If you have income from more than one job, or from both self-employed and employment, you could be paying National Insurance (NI) on both.
In such a case, for 2025/26, you can complete form CA72A at www.gov.uk/defer-national-insurance and send it to HMRC before 14th February 2026 – then:-
If you have: two or more jobs and earn more than £967 per week (£4,189 per month) in one of the jobs over the year, OR you earn more than £1,209 per week (£5,237 per month) for two or more jobs combined, HMRC will notify one of your employers to deduct Employee’s National Insurance at only 2% instead of 8%;
If you are self-employed AND employed, then HMRC will automatically defer the NI (class 2 & 4) on your self-employment income when you submit your Self-Assessment Tax Return.