In the UK people can self-certify as being unfit to work for up to 7 days, after which they need a "fit note" (which is more commonly called a "sick note") from

In the UK people can self-certify as being unfit to work for up to 7 days, after which they need a "fit note" (which is more commonly called a "sick note") from a healthcare professional. Additionally workers are guaranteed £109.40 ($139.33) a week in statutory sick pay (paid by the employer) for up to 28 weeks of time off for illness. For contrast, the median weekly full-time income is £640 ($815) so it's potentially a big drop in pay for being off work sick - we have one of the lowest rates in developed nations - but it's better than getting nothing.