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HMRC internal manual

National Insurance Manual

NIM10011 - Aggregation of Earnings: Calculating NICs: General

 

Once it has been established that earnings fall to be aggregated, NICs are calculated based on total earnings received from the respective jobs, i.e. the total earnings received are treated as being a single payment of earnings for a single employment. The employer must use the earnings band and percentage rates relevant to the aggregated earnings to calculate NICs.