I found out my employer did not with hold the maximum HSA deduction in 2018. Can I make a payment before April 15 and get the tax benefit myself?

[JohnW15 · Accepted solution]

Yes, you can.  You have until the regular due date of your 2018 tax return, April 15th 2019, to make HSA contributions for 2018.

Make sure that you identify to the HSA custodian that the contribution is for 2018 since, by default, they'll assume that the contribution is for 2019.