Payment of income tax on rental income and interest earned.

I have some rental income that I would like to invest monthly in my fixed deposit. I know I must pay tax on both the rental income and the interest earned but when? I have to fill in a tax return twice yearly as a provisional tax payer. If the rental income and interest is fixed into the deposit account and I am not allowed to withdraw money, how would I go about paying the interest? Should I keep funds separate specifically for this in another account.

Provisional tax is paid twice annually on 31st August and 28th of Feb. You need to register as a provisional taxpayer when your taxable income, that is your profits from the rental and the taxable interest are more than R30 000.