During the 2019 assessment period I've contributed too much money towards my retirement. This resulted in an amount of R 26555 being carried-over.
I would like to top-up my retirement annuity for the 2020 assessment period to fully utilize the 27.5% deduction threshold.
Should I subtract the carried forward amount from the top-up amount or can I ignore it and pay the full 27.5% towards the annuity?
Yes, subtract the carried over amount. You can of course contribute 27.5% of your 2020 FY income, and the R 26,555.00 will be carried over again, where it will grow tax free.