Checksum question

I had always assumed an HP tune did NOT correct the checksum, therefore I cannot pass smog in California where the smog station checks for that, but I'm just assuming.
So does it or does it not?

I've been driving around with the oem tune in the car for a couple months now, while I tinker and in case my check eng light goes out, and I'm rather sick of it. It would be nice if the HP tune was good and I don't need to worry.
If the answer is no, then what would be a good tool to correct the checksum? I have a KESS, and info I could fine was fuzzy at best about doing that, or maybe just above my pay grade.

I assume you read the oem ecu to get the correct checksum, then some hardware/software simply writes it into the tuned version? Or maybe it's not that simple? I dunno, can someone enlighten me? Please? :)