It is generally where you are stationed...unless there temporarily (like in Basic training)
The "Mailing Address" is just where you want any communications from the IRS to go ( and your home state to go if you are required to file there). It is also the address where the IRS will send a paper-check refund if you choose that, or if there is any problem with a Direct-Deposit that fails.
Mailing Address also does not set your HOR/SLR (state of legal residence) that you entered with the series of questions when you entered your name and SSN..
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IF you get PCS'd before you get your refund (if getting a refund), you will have a to make sure you give the post office a mailing address forwarding form.
And there is also an IRS change of address form if you happen to get PCS'd just after filing your taxes..but no need for that if you are remaining where you are now for the next 6 months, or more.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
