[1] Labour remained in control of the council, though lost thirteen seats overall, while Plaid Cymru doubled their numbers to eighteen.
[6] A by-election took place on 5 December 2019 after Plaid Cymru councillor, Darren Macey, resigned his seat because of a conflict of interest with his new job for RCT Sporting Heroes.
[7] A by-election took place on 6 May 2021 after a Conservative councillor, Mike Diamond, resigned his seat for personal reasons.
[8] A by-election took place on 6 May 2021 to fill a vacancy after Cynon Valley Party councillor, Gavin Williams, was removed from his position after being absent from council meetings for more than six months.
[10] A by-election took place on 22 July 2021 following the death of long-standing Labour councillor, Clayton Willis.