Hi Robert Anderson,
You should complete P85 when you leave the UK providing all details regarding your departure from the UK.
If you are continuing to be paid by a UK employer we will consider if a code of NT (No Tax) is applicable.
You should also take the Statutory Residence Test on Gov.UK to determine where you will be classed as resident in the year of departure.
Get your Income Tax right if you're leaving the UK (P85)
RDR3 Statutory Residence Test