What should I do about my HSA regarding taxes?

Before you do anything, you should verify everything.

Is the plan single or family (which is anything that isn't just you)?

Where you in the plan for all 12 months, or for less?

How much, if any, money did you put in through work?

What was on the W-2 in box 12 with code of W?

How much, if any, money did you contribute by writing a check and sending it in?

Did you have an HSA in 2014?

How much did you contribute to the account from 1/1/2015 to 4/15/2015 that wasn't through work and that you claimed for 2014?

How much did you contribute to the account from 1/1/2016 to 4/15/2016 that wasn't through work and that you intend to claim for 2015?

Have you received your 5498-SA? What was on it?

Note, the 5498-SA is NOT officially a source document for the form 8889. In fact you aren't supposed to get it until sometime in May. Box 2 and 3 on the form can cover multiple years and are for IRS use only.

If you actually had an excess contribution, was it through work or from you? See the instructions for the form 8889 and 5329 on how to report it.

To follow up on nina's comment, look at the form 8889. Line 2 is for contributions you made directly to the HSA custodian. Line 9 is for contributions you (and your employer) made through work. Many people try to use line 2 instead of line 9--and the software is supposed to pickup line 9 from the W-2. Other people fail to fill out 8889 at all and when that happens, the software tries to add the income back on line 21.

It is easy to mess up HSA contributions and distributions on a tax return. It is unusual for excess contributions to be made especially when you contribute through work.

The most common mistake is to fail to enter that you spent the money on medical expenses. Also, failure to indicate the correct type of coverage (self or family) or the months you had the plan.

Another easy way to make a mistake is to enter your employer contribution as a direct contribution. Employer contribution means the amount shown in Box 12 of your W-2 with a code of W. Do not enter this as an after-tax contribution or you will generate a phantom excess contribution.

how could you possible contribute more than was allowed? your employer should have let you know that when you chose the amount to contribute for 2015 way back in fall of 2014