It's the detail that counts when becoming resident

When deciding if you are UK resident, you need to consider the number of days you are present in the UK and the ties that you have in the UK.  

With people going into self-isolation and being unable to travel, you may end up spending longer in the UK than you ever intended.  There are provisions that allow longer stays to be disregarded due to exceptional circumstances and HMRC have helpfully confirmed that if you:

• are quarantined or advised by a health professional or public health guidance to self-isolate in the UK as a result of the virus
• find yourself advised by official Government advice not to travel from the UK as a result of the virus
• are unable to leave the UK as a result of the closure of international borders, or
• are asked by your employer to return to the UK temporarily as a result of the virus

the circumstances are considered as exceptional.  

This will give a partial solution but there may still be consequences that will be felt for some time.  For example, exceptional circumstances apply in counting the number of "days spent" in the UK but not the number of days working.  So if you have to stay in the UK but use your time to continue working, this may affect whether you become UK resident.  

No more than 60 days can be disregarded as "exceptional" in any tax year.  Although the new tax year begins on 6 April so days between now and 6 April will not count to the 60 day disregard, with there being talk of lockdown possibly continuing for three months, or even longer, 60 days may not be enough.   

In addition, you may wish to be UK resident  (for example because you wish to avoid becoming resident in another jurisdiction, or you want to continue contributing to an ISA) but are currently stranded overseas.  In this case, there is no provision to extend the number of days treated as spent in the  UK and, with the residence test now being statutory, there does not appear to be any discretion for HMRC to accept that you would have been present in the UK for longer had this been possible.  If you are in this position, once travel becomes possible, you may need to come back to spend some time in the UK to make sure that you can maintain you residence.  

What is clear is that, unless steps are taken to amend the legislation, if you are relying on "day-count" to determine whether you are, or are not, UK resident you will have to have a careful look at you position once the situation has returned to something more normal.