SolvedNIM06270 | Class 1 NICs: Expenses and allowances: Travelling expenses: Temporary posting away from a permanent workplace: Limited duration - the 24 month rule
From HM Revenue & Customs · National Insurance Manual
Paragraph 3 of Part VIII of Schedule 3 to the Social Security (Contributions) Regulations 2001
General
As explained in NIM06265 a place an employee attends for the purpose of performing a task of limited duration or for some other temporary purpose is a temporary workplace. But a special rule prevents a workplace being a temporary one where an employee attends it in the course of a period of continuous work which lasts, or is expected to last, more than 24 months. Where this rule applies the workplace will be a permanent workplace.
A period of continuous work is a period throughout which the duties of the employment are performed to a significant extent at that place. To apply this rule treat duties as performed to a significant extent if the employee spends 40% or more of their working time at that place.
Where the employee has spent, or is likely to spend, 40% or more of their working time at a particular workplace over a period of more than 24 months the workplace is not a temporary workplace and must therefore be treated as a permanent workplace. Any travel between home and that place will be ordinary commuting and will not satisfy the exclusion provided by paragraph 3 of Part VIII of Schedule 3 to the Social Security (Contributions) Regulations 2001.