It's a stupid story and my own damn fault but anyway.

I've been running as a sole proprietor for a while now (3 years or so) but with minimal income - the last accountant I spoke to assured me that I had no need to register for provisional tax (!) and I didn't think to check up on it until this year when I started earning a bit more. The extra complication is that I am employed full time as well so from what I've read, I'm clearly supposed to be paying provisional tax!

I really don't want to get on the bad side of SARS but I'd already filed my personal tax return for this year when I found out about provisional tax. What do I do now?

Obviously I'd like to avoid penalties and so on but dammit, SARS is the one govt. department that I really, really don't want to piss off.

tl;dr: Earning as sole prop, employed full time. Not registered as provisional tax payer. Have filed personal return already - what do I do?