In the situation where an employer who chooses to reimburse an employee for the cost of a relevant coronavirus antigen test, and employees who are reimbursed for the cost of a relevant test from their employer, HMRC have confirmed that these payments will be disregarded from National Insurance contributions for the employee and employer
To be eligible for the disregard, a relevant coronavirus antigen test is defined as a test which can detect the presence of a viral antigen or viral ribonucleic acid (RNA) specific to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
The disregard will apply to any advance payments or reimbursements made to an employee for the cost of a relevant coronavirus antigen test made on or after 25 January 2021, until 5 April 2021. For any relevant advance payments or reimbursements which have been made during the 2020-21 tax year, but before this measure comes into force, HMRC will exercise its Collection and Management powers and will refrain from collecting any National Insurance contributions or Income Tax due on the reimbursement of a relevant coronavirus antigen test.
The intention is to legislate a corresponding Income Tax exemption in the next Finance Bill to prevent an equivalent tax charge on the payments
More details can be found here.