Can I insist on a negative COVID-19 test result before an employee returns to work?

If an employee has self isolated due to contact with a positive test case, or when asked to do so by Test and Trace, or if they have had a positive test result (whether symptomatic or asymptomatic), we all know that they must self isolate for 10 days from the date of the request, or the positive test result.
At Robinson Grace HR, we have been fielding questions from a number of clients about whether it’s acceptable to insist on a negative test result before agreeing to staff returning after a COVID-19 related absence.
The advice is for employers is to carry out temperature checks if they are concerned but not to insist on a negative COVID-19 test before employees return to work*, but instead to follow these guidelines:
Those who never developed symptoms can end isolation 10 days after testing positive.
Those with moderate to mild symptoms can end isolation after 10 days if at least 24 hours have passed without a fever and other COVID-19 symptoms (such as the cough), have improved.
Those with severe symptoms may need to continue isolation for a full 20 days or longer, and certainly until their temperature has returned to the normal range for at least 24 hours.
Employers often want the reassurance of a negative test result, but people can test positive for COVID-19 for 90 days after infection due to infection particles still being present, long after they are no longer contagious.
*There is however separate advice for employees returning to work in health care or critical infrastructure businesses where introduction of COVID-19 could cause a major disruption. In these settings, employers are within their rights to apply more stringent criteria, i.e. a higher recovery threshold or a negative test result to prevent transmission, for returning workers.