FHSA
FHSA gets 8k contribution room per calendar year.
FHSA can carry over a maximum of $8,000. This means the most contribution room you can have at once is $16,000. (ie, if you only deposit 4k during 2024 you would only have 16k again in 2025 instead of 20k).
The deadline to contribute for your taxes is Dec 31.