Your HSA contribution for 2015 made in 2016 was reportable on your 2015 tax return.  It is not reportable on your 2016 tax return unless it was an excess contribution reported on your 2015 tax return.

If you failed to report contribution for 2015 on your 2015 tax return, you must amend your 2015 tax return, otherwise the IRS will treat it as an excess contribution that is subject to penalty.

It depends.

You could contribute to your HSA for 2015 up to April 15, 2016.

If you had elected to count the January 2016 contribution as a contribution for 2015 and had already deducted it in your 2015 return, then you cannot deduct it again in 2016.

Edited on Feb 1, 2017  6:22 PM CT