What Do I Need to Do Before September 15?
If your S Corporation or partnership filed an extension earlier this year, that extended deadline is approaching. For calendar-year businesses, September 15, 2026, is the deadline to file an extended Form 1120-S or Form 1065 return.
Now is the time to make sure your tax preparer has everything needed to complete the return—not September 14.
When Is My Extended S Corp or Partnership Tax Return Due?
Short Answer
September 15, 2026. If your calendar-year S Corporation or partnership received a six-month filing extension, September 15 is the deadline to file the return.
If your return hasn't been completed yet, check with your tax preparer now to make sure there isn't information or documentation still needed from you.
What Should I Have Ready?
Every business is different, but here are some of the items you should make sure your tax preparer has before the filing deadline:
- Complete income and expense information for the year
- Reconciled business books and financial records
- Bank and credit card information requested by your tax preparer
- Information about major equipment or asset purchases
- Details about any assets sold or disposed of during the year
- Information about new loans or significant changes in business debt
- Details about ownership or partnership changes
- Current shareholder or partner information
- Responses to any outstanding questions from your tax preparer
If something unusual happened in the business during the year, make sure your tax preparer knows about it. Don't assume they'll see it simply by reviewing the numbers.
Quick Tip: Check your email and client portal for outstanding requests from your tax preparer. One missing document or unanswered question can hold up completion of the entire return.
Why Does the September 15 Deadline Matter to the Owners?
Your business return and your personal tax return are connected. S Corporations and partnerships are generally pass-through entities. Once the business return is completed, each shareholder or partner receives a Schedule K-1 reporting their share of the business's income, deductions and other tax items.
That K-1 is then used to complete the owner's individual income tax return. If the business return isn't finished, the owners may not have the information they need to complete their personal returns before the October 15 individual extension deadline.
Does an Extension Give Me More Time to Pay?
An extension gives you additional time to file a tax return. It generally does not extend the original deadline for paying taxes that were due. That's an important distinction, particularly for business owners whose income passes through to their individual returns.
If you're concerned about a balance due, estimated payments or whether you've paid enough during the year, talk with your tax advisor rather than waiting until the return is filed.
What Should I Do Now?
If Barklee is preparing your extended S Corporation or partnership return, make sure we've received everything requested from you.
Review your records, respond to outstanding questions and let us know about anything significant that happened in the business during the year.
The earlier we have complete information, the more time we have to prepare and review the return properly before the September 15 deadline.
How Barklee Can Help
Tax extensions provide additional filing time, but that extra time goes quickly. Barklee Financial Group works with business owners to make sure their returns are complete, accurate and ready for filing. If you're unsure whether we've received everything needed for your return, reach out to the Barklee team now.
