IRS Publication 17 — Your Federal Income Tax (Individuals)
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“Underpayment Penalty for 2025 If you didn’t pay enough tax, either through with- holding or by making timely estimated tax pay- ments, you will have an underpayment of esti- mated tax and you may have to pay a penalty.”
You must include your SSN in the correct place on your tax return. P .O. box. If your post office doesn’t deliver mail to your street address and you have a P .O. box, enter your P .O. box number on the line for your present home address instead of your street address. Foreign address. If you have foreign address, enter the city name on the appropriate line. Don’t enter any other information on that line, but do complete the spaces below that line (Foreign country name, Foreign province/state/ county, and Foreign postal code).
Don’t abbreviate the country name.
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