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HMRC internal manual

National Insurance Manual

Class 2 National Insurance contributions liability: Contribution week

Regulations 1(2) and 155 of the Social Security (Contributions) Regulations 2001 (SI 2001 No 1004)

Where a person is liable to pay Class 2 National Insurance contributions (NICs), Class 2 NICs are due for each contribution week or part of a week that a person was self-employed. So, where a person was self-employed and liable to pay Class 2 NICs for part or all of one day in a week, liability arises for one week’s NICs due at the weekly flat rate.

A ‘contribution week’ is defined as a period of seven days beginning with midnight between Saturday and Sunday. The first day of the contribution week is Sunday and Saturday is the last. The first week of the contribution year starts on the first Sunday after 5 April.

So, for example, the first contribution week of the 2011/12 contribution year starts on Sunday 10 April 2011 and ends on Saturday 7 April 2012. Some contribution years will include 53 contribution weeks.