I've heard that it's bad to flush cat poop down the toilet but I've done it for years with my cats and never had a problem clogging the toilet or anything.
If human poop can go down the toilet then so can cat poop without it being a problem.
If you have regular cat litter just avoid flushing too much cat litter down the toilet along with the cat poop and you should have no problem flushing the cat poop down the toilet.
They do make and sell some flushable cat litter that prevents clogs in the toilet and drain lines though.