If your LLC, S-Corp or C-Corp operates on a fiscal year that ends September 30, 2026, you have exactly 45 days to close cleanly. It's not a made-up date: according to the IRS, corporations whose fiscal year ends in September must file their return (Form 1120 or 1120-S) by January 15, 2027, with an extension until July 15, 2027. But the real work starts now, and what you do in these 45 days determines whether you close with structure or in a rush.
Why September matters more than you think
Most businesses operate on the calendar year (January–December), but roughly 18% of U.S. corporations use a different fiscal year, according to IRS data published in its Statistics of Income 2024. Among service professionals and consultants, that percentage is higher: many choose a September fiscal year-end because it lines up with the start of their busy season (October–December) and lets them plan taxes with a clear head.
If you chose this calendar, it wasn't by accident. It was to gain an operational advantage. But that advantage only works if you close the year with discipline.
Weeks 1–2 (now through September 14): close operations and reconcile
Before you touch the numbers, your operations need to be closed. That means:
- Stop new credit sales for this fiscal year. If you invoice on September 28 and collect in October, that income falls into the next fiscal year. Decide whether that works in your favor.
- Record all deductible expenses for August and September. Equipment purchases, vendor payments, annual subscriptions. If you pay before September 30, you deduct it this year. If you wait until October, you deduct it next year. Choose based on your strategy.
- Reconcile all bank accounts. Every transaction from July, August and September must be reflected in your accounting software. According to a 2025 QuickBooks Enterprise study, 42% of errors on corporate returns come from unreconciled transactions in the last 90 days of the fiscal year.
Week 3 (September 15–21): adjust inventory and assets
If your business carries physical inventory (retail, distribution, manufacturing), now is the time to do a physical count. The difference between what your system says and what you actually have in the warehouse is an adjustment that affects your profit. Do it now, not in December after you've already filed.
If you bought equipment, vehicles or machinery this fiscal year, check with your accountant whether you applied Section 179 or bonus depreciation. Under the Tax Cuts and Jobs Act, in effect through 2026, you can deduct up to $1,220,000 in new or used equipment (2026 limit per IRS Rev. Proc. 2025-17). But that benefit starts phasing down in 2027. If you were planning to buy something else, you have 9 days.
Week 4 (September 22–28): payroll, contributions and distributions
- Employee bonuses and commissions: If you're going to pay them, do it before September 30 to deduct them in this fiscal year. If not, wait until October and deduct them next year.
- Retirement plan contributions: Profit-sharing and SEP IRA contributions for your fiscal year ending in September can be made up to your return's due date (with an extension, July 2027). But if you want to reduce your reported profit now, some strategies require decisions before year-end.
- Distributions to partners (S-Corp or multi-member LLC): If you decide to distribute profits, the amount and the date matter. Distributions affect each partner's capital basis, and that changes how much you can deduct in losses, if there are any. According to National Society of Accountants data (2025), 34% of S-Corps adjust distributions in the last two weeks of the fiscal year to optimize basis.
Weeks 5–6 (September 29 to October 14): close the books and produce financial statements
Your fiscal year ends on September 30. The next one starts on October 1. But your books don't close themselves.
- Accruals: Income earned but not yet invoiced, expenses incurred but not yet paid. This isn't optional: it's GAAP (Generally Accepted Accounting Principles). If you skip it, your balance sheet lies.
- Official financial statements: Balance sheet, income statement, statement of cash flows. You need them for your return, for banks if you apply for credit, and for investors if you have them.
- Review your effective tax rate. Compare your projected profit against the estimated payments you made during the year. If you underpaid, you'll owe in January. If you overpaid, you'll get it back. According to the IRS Data Book 2025, 29% of small corporations (under $10M in revenue) pay underpayment penalties because they didn't adjust their quarterly estimates.
What happens if you're late
If September 30 catches you with messy books, you'll still close. But you'll close badly. You'll estimate, you'll guess, and you'll pay for it:
- Deductions you lose because you didn't document them in time.
- Accountant adjustments in February that force you to amend your return.
- Underpayment penalties if you underestimated your real profit.
The IRS charges daily compound interest on unpaid taxes. In 2026, the rate is 8% per year (per IRS Notice 2026-15). It's not catastrophic, but it's avoidable.
What to do this week
It's September 2026. You have 45 days or less. Here's what to do today:
- Open your accounting software and check how many August and September transactions are unreconciled. If there are more than 20, block off 3 hours tomorrow to clean them up.
- Talk to your accountant. If they haven't reached out yet to prepare the close, reach out to them. Ask what they need from you and when.
- Review your list of large pending expenses (equipment, services, annual subscriptions). If any of them can be deducted this year and you need it anyway, pay it before the 30th.
- If you have employees, confirm with payroll that all September payments will be processed before the close. A late payment that lands in October is an expense for the next fiscal year.
Don't wait for your accountant to rush you. In September, accountants who handle alternative fiscal years are swamped. You're the one in control of your close. Your accountant only works with what you give them.
References
- IRS Statistics of Income, Corporate Income Tax Returns 2024 (published March 2025)
- QuickBooks Enterprise, "Common Accounting Errors in Small Business Year-End Close" (2025)
- IRS Revenue Procedure 2025-17, Section 179 Deduction Limits
- National Society of Accountants, Small Business Tax Planning Survey 2025
- IRS Data Book 2025, Table 17: Corporate Estimated Tax Penalties
- IRS Notice 2026-15, Interest Rates for Underpayment and Overpayment
Want us to review your situation before September 30? At La Familia Multiservices we help business owners in Florida close their fiscal year with no surprises. Book a consultation at www.lafamiliamultiservices.com.
