The online service was launched on 26 May for small and medium-sized employers to recover statutory sick pay (SSP) payments they have made to their employees.
Employers will be able to make their claims using the online service and tax agents will also be able to make claims on behalf of employers.
Employers are eligible if they have a PAYE payroll scheme that started before 28 February 2020 and they had fewer than 250 employees before the same date.
All types of employment contracts are covered including employees on agency contracts and on flexible or zero-hour contracts.
The repayment will cover up to two weeks of SSP and is payable if an employee is unable to work because they have coronavirus, are self-isolating and unable to work from home, or are shielding.