I had a high deductible plan the first 4 months of the year. am I eligible to use my HSA as a write-off?

[BMcCalpin]

Once you left the HDHP, you could no longer contribute to the HSA. However, contributions during those first four months would be valid, if you don't exceed the limited annual HSA contribution limit.

Your annual HSA contribution limit would be reduced to 4/12ths of the normal annual limit.

On the other hand, even though you are no longer in the HDHP, you still keep your HSA. You can continue to take distributions from the HSA for qualified medical expenses until the HSA is exhausted.

Note that for any year in which you make contributions (if allowed) or take distributions, the IRS requires you to attached a completed form 8889 to your return, which means that you will need to complete the HSA interview (Federal Taxes->Deductions & Credits->Medical, click on "HSA MSA Contributions").