Hi - my name is XXXXX XXXXX I'm a litigation
attorney. Thanks for your question, but I'm sorry for your trouble.
The only way to avoid the penalty is to file a written request with the board for a variance on the monthly dues deadline, and explain your situation. Usually, a board will make an exception if there is a legitimate reason for it.
However, if the board refuses, you can be filed the assessment. It's not really that you're being penalized for being disabled or because you're on a fixed income AS LONG AS the HOA applies the penalty to everyone equally.
IF the board refuses you, it may be that you could try to get ahead on your payments one month. Then, when you receive your money mid-month, you could go ahead and pay for the next month's dues - - so you'll be a few weeks early rather than being late. I know that may be a hardship for one month, but that's a possible solution IF the board turns you down.
However, going to the board and asking for a variance in the rules is the best place to start.