Gov.uk Guide on Absence at work

​Certifying absence from work
By law, medical evidence is not required for the first 7 days of sickness. After 7 days, employers may use their discretion around the need for medical evidence if an employee is staying at home.
We strongly suggest that employers use their discretion around the need for medical evidence for a period of absence where an employee is advised to stay at home either as they are unwell themselves, or live with someone who is, in accordance with the public health advice issued by the government.
If evidence is required to cover self-isolation or household isolation beyond the first 7 days of absence then employees can get an isolation note from NHS 111 online or from the NHS website.
What to do if an employee needs time off work to look after someone
Employees are entitled to time off work to help someone who depends on them (a ‘dependant’) in an unexpected event or emergency. This would apply to situations related to coronavirus (COVID-19). For example:

• if they have children they need to look after or arrange childcare for because their school has closed
• to help their child or another dependant if they’re sick, or need to go into isolation or hospital

There’s no statutory right to pay for this time off, but some employers might offer pay depending on the contract or workplace policy.