A tax extension gives a business or individual additional time, typically six months, to file a tax return, but it does not extend the deadline to actually pay any tax owed.
This distinction trips people up constantly: filing Form 7004 (for a business) or Form 4868 (for an individual) pushes back the filing deadline, but any tax that isn't paid by the original due date still accrues interest and potentially penalties, calculated as if the extension had never been filed.
An extension is genuinely useful when the return itself needs more time, waiting on a final K-1, finishing a complex calculation, but it's not a way to defer an actual tax payment without cost. Estimating and paying what's likely owed by the original deadline, then filing the completed return later, avoids the interest that comes with guessing low.
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