Statutory Sick Pay
If you’re unable to work due to illness or are self-isolating due to Corona virus, and your employer doesn’t offer contractual sick pay, you can claim Statutory Sick Pay (SSP) if you usually earn at least £118 per week before tax. For the next 3 months at least, you can claim SSP from the first day of not working. Your employer pays SSP and you should tell them immediately, and at least within 7 days, that you need to claim it. You normally have to provide a GP fit note after 7 consecutive days of illness but at present you only need to provide a note from NHS 111 online:
https://111.nhs.uk/