The rules are –

‘A vacancy at an election may arise if the number of candidates nominated for election are too few to warrant an election or to fill all the vacant seats. This vacancy is dealt with by co-option.

If sufficient candidates have been nominated to form a quorum (normally three councillors in the smallest parish councils or one-third of the total number of councillors), they will co-opt councillors to fill the vacant seats. Vacancies must be filled within 35 days (not counting Christmas Eve, Christmas Day, Good Friday, bank holidays, any day appointed for thanksgiving, Saturdays and Sundays) from the date of the election’.

Further information can be found at –Notice of Vacancies in the Office of Councillor, Loatland Ward (May 2021) – Desborough Town Council