I have an HSA for which I made prior year contributions last calendar year (contributions for 2016 made in 2017 before the filing deadline), current year contributions (contributions for 2017 made in 2017) and more prior year contributions made this year (contributions for 2017 made in 2018).
Let's say I made a $2000 contribution in 2017 for 2016 and another $2000 contribution for 2017 in 2017, then a $1000 contribution in 2018 for 2017. My total contributions for 2017 are $3000, which is less than the maximum contribution, but my 5498-SA would show $4000 in Box 2 because the IRS instructions say to include all contributions made during the 2017 calendar year.
Does this mean that I need to withdraw $600 from my HSA before the filing deadline to avoid the excess contribution tax, bringing me to $3400 (the individual maximum for 2017)?
What can I deduct on my 2017 taxes, $4000 or $3000?
I'm a bit confused as to whether Box 2 tracks whether or not I made excess contributions for a year or just what I can deduct for that year.
Follow up questions:
Does this mean that, in the future, I can contribute $3400 (pretending the maximum remains $3400) in January for the prior year and $3400 for the current year, then claim a $6800 deduction for the current year taxes?
Would this then mean that in the following year, I could only claim up to $3400 in deductions for that particular year because I can't claim a prior year contribution as a deduction?