What an extension does
Form 4868 (individuals) and Form 7004 (entities) extend the time to file by six months — generally to October 15 for individual returns, September 15 for partnerships and S-corps, and October 15 for C-corps. The extension is automatic — no IRS approval needed.
What an extension does NOT do
Extensions do not extend the time to pay. Tax owed is still due on the original due date (April 15 for individuals). Pay an estimated balance with the extension to avoid the failure-to-pay penalty (0.5% per month) and to minimize interest.
Why extend
You're waiting on K-1s from partnerships or S-corps that don't arrive until September. You need more time to organize records. You're negotiating a complex tax position. You're funding a SEP-IRA contribution for the prior year. Most professional preparers file extensions for nearly all small-business clients to give breathing room and reduce the risk of error from time pressure.
The "audit risk" myth
Extending does NOT increase audit risk. The IRS uses a Discriminant Inventory Function (DIF) score and other selection criteria that have nothing to do with the filing month. Filing in October is no more (and no less) auditable than filing in April.
When NOT to extend
If you expect a large refund, file by April 15 to receive it sooner. If you have a complete and clean return ready, file it. If your state requires a separate extension, ensure that's filed too — federal extension does not automatically cover state in every state.
How experienced filers approach this
Experienced self-employed filers and the CPAs who advise them treat this question as a recurring planning exercise rather than a one-time decision. They model the multi-year tax impact rather than just the current year, document the reasoning in a short workpaper that survives staff turnover and software changes, and revisit the analysis annually as facts and laws change. The discipline is not difficult — a half-day in January with last year's return, the current-year IRS publications, and a spreadsheet — but it is rare among DIY filers, which is precisely why it produces outsized results.