In Texas, that info is on our seller disclosures. If I'm lucky, I'll search and find one filled out. Otherwise, I'll do a quick search of the internet to see if the HOA is online.
I do not waste a lot of time on this. If all else fails, I'll take a consensus of the MLS data sheets and choose the HOA fee that seems to be the most accurate and then I'll put a disclaimer in my report that this is an estimate of the annual fee due, taken from information available in the MLS.
When I do find information that I know to be 100% accurate, I write it down. That way I have it for future record.