answer:Judging by the way my insurance has it working it seems pretty simple. When up for enrollment, I tell work that for the HSA I want X amount of dollars saved up during the next year. With each paycheck, $(X/24) dollars gets taken out of my pre-taxed check and goes into the HSA. Once i accrue some medical expenses (copays, labwork, perscriptions), I send receipts of the bills to the people that handle it, and I get reimbursed through direct deposit. I can also get reimbursment of funds even though there may not be immediately enough in the account assuming it’s under the yearly limit. The only drawback is that you MUST use the funds you’ve saved up by year’s end, or else you forfeit all of it. The next year it reboots to 0, so planning expenses and what to save is extremely important.