Visit Internal Revenue Service and search for the instructions for Form 8889.Pay attention to the rules over the limits to contributions which involve the full calendar months within an eligible high deductible health insurance program AND your full year limits, combining both your contributions and those of your employers.The employer that allows payroll deductions directed to an HSA will subtract the amount, as pre-tax dollars. To avoid double-counting, those contributions will not reduce federal income as an entry on line 26 of Form 1040.This question is put up mid-calendar year, suggesting a mid-year change in insurance. From personal experience, the major concern is the portion of the deductible already paid by the person before the job change/severance.Under COBRA, your year to date out of pocket expenses are kept as a running total. If you switch to a Marketplace plan mid-year, your deductibles reset to zero. You get no credit for $1,500 in medical expenses during the first half of the year, but begin a new, fractional year plan at zero dollars out of pocket year to date. The deductible is not pro-rated. In other words, with just four months left in the year, you need to incur the expenses of a full year out of pocket to ever see any benefit from your new plan.It is probably more likely far better to wait until open enrollment and the calendar year of your new employer than to switch. The only difference is for the very healthy who have not had any medical expenses at all so far this year.