There is a relaxation to the residence day counting rules if you have been forced to spend days in the UK due to Exceptional Circumstances. Up to 60 days a year can be counted as being here under Exceptional Circumstances and therefore not counted as residence days. Note that workdays are never counted as being for Exceptional Circumstances, so it is not possible to say you have only worked here for more than 40 days due to COVID-19 and lose the Work tie.
Traditionally, Exceptional days relate to births, deaths, sudden and life-threatening illness or injury of the taxpayer or a close relative. However, the Revenue has now issued a little guidance about the current COVID-19 implications for Exceptional Circumstances, and said it can be applied in the following circumstances:
The Revenue have noted that events resulting from the impact of the virus are changing rapidly and this guidance may change at short notice as situations change. I can keep you up to date of any relevant changes but for now they should apply enough to your situation.
Please note that one important proviso for days to be treated as Exceptional is that after the Exceptional Circumstance is resolved, a taxpayer must intend to and in fact leave the UK as soon as practicable.
Similar legislation has been enacted in the US, with the IRS publishing guidance that individuals who intended to leave the US in the period between 1 February and 1 April 2020 but were unable to do so due to COVID-19 related reasons may exclude up to 60 days of presence in the United States for the purpose of applying the substantial presence test.