September 15 is a hard deadline—and it arrives faster than most business owners expect. If you or your CPA filed an extension earlier this year, the clock is ticking on your final return. You’re juggling quarterly sales tax deposits, payroll, invoicing, and growth. The last thing you need is to wake up on September 16 and realize your CPA never heard back from you because you forgot to send the bank statements, or you left a critical expense receipt sitting in your email drafts. This checklist walks you through exactly what your CPA needs from you—and when—so neither of you scrambles at the deadline.
Does this sound like you? You’re spending billable hours on data entry instead of advisory work. See how the platform handles the categorization for you — free for your first client’s first period, no credit card.
Does this apply to your business in Florida?
If you filed a federal income tax extension (Form 7004 or equivalent) for your sole proprietorship, partnership, S corporation, or C corporation, September 15 is your absolute final due date to file your completed return. The Florida Department of Revenue also sets September 15 as the deadline for certain Florida corporate tax returns and fiduciary returns claimed under federal extension. If you didn’t file an extension, your return was due by April 15; this deadline does not apply to you.
Why September 15 matters more than you think
The difference between filing on September 14 and September 16 is the difference between compliance and a penalty. The IRS treats September 15 as a drop-dead date—no grace period, no late-filed return discount. If your CPA misses it, you’re exposed to failure-to-file penalties before you’ve even reviewed the numbers. Worse, a late filing can delay any refund you’re owed, create issues with your sales tax compliance, and raise questions during an audit years later. The extension bought you time; September 15 is when that time runs out.
What your CPA actually needs from you before September 15
Your CPA doesn’t need a novel—they need data, organized by category. Here’s what they’re waiting for:
- Bank and credit card statements for every account used in the business, from January 1 through December 31 of the tax year.
- Reconciliation or explanation of any large, unusual, or unclear deposits or withdrawals.
- Invoices and receipts for claimed deductions (meals, travel, equipment, repairs, office supplies).
- Payroll records if you have employees: W-2s issued, payroll tax deposits made, and any 1099s for contractors paid over $600.
- Sales tax records if applicable in Florida: monthly returns filed, amounts collected and remitted, any exemption certificates for resales.
If you use Outsourcing Processing to organize your transaction data, your CPA can pull categorized reports directly rather than reconstructing your year from scattered documents. If not, gather copies of everything into a single folder (physical or digital) and send it over now.
The two-week warning system: build this into your workflow
Don’t wait until August 31 to collect receipts. Set a calendar reminder for August 15—five weeks before the deadline. On that date, send your CPA an email listing what you’ve already provided and asking for a checklist of what’s still missing. This gives them two full weeks to ask follow-up questions and gives you time to find or generate the missing pieces. If you’re working through sales tax compliance in parallel, early communication also ensures your CPA and tax advisor are not working at cross-purposes.
How to organize receipts and records so your CPA doesn’t have to hunt
Your CPA will review what you send. If half your receipts are blurry phone photos with no dates, they’ll ask you to re-send or clarify—burning time you don’t have in early September. Instead, use this structure:
- Create a folder for each expense category: Meals & Entertainment, Travel, Equipment, Office, Utilities, Repairs, Contractor Payments, etc.
- For each receipt, note the date, amount, vendor, and purpose in a simple text file or spreadsheet (or let your transaction platform categorize it for you).
- For large purchases (equipment over $500, vehicles, property improvements), include a one-sentence note on what it is and when you bought it.
- For contractor payments, ensure you have the contractor’s name, address, and tax ID—your CPA needs this to issue 1099s correctly.
Clear, organized records aren’t just courteous—they speed up the review, reduce the chance of missed deductions, and lower the risk of back-and-forth emails right before the deadline.
Sales tax extension deadlines: don’t mix them up
If you operate in Florida and collected sales tax, you may have also filed for a sales tax extension separate from your income tax extension. These are different deadlines. Florida sales tax returns typically are due by the 20th of the month following the month of sales—but if you claimed an extension, confirm with the Florida Department of Revenue exactly when your final return is due. It may not align with September 15. Communicate early with your CPA about whether you need to file Florida sales tax separately and what the real deadline is.
Common mistakes—and how to avoid them
Mistake 1: Assuming “extension” means you have until December
An extension is not a gift of six extra months. It’s a filing extension—the deadline to file the return shifts, but tax is typically still due by April 15 (or the original deadline). If you owe, interest and late-payment penalties start accruing on the original due date, not September 15. Your CPA can explain your actual tax liability on your final return, but September 15 is always about submitting the return itself, not settling the bill.
Mistake 2: Sending half the records now and half in August
Your CPA can’t prepare a return in two passes. Each time you send a new batch of records, they reset their work. Send everything at once in early August. If you discover a receipt in late August, send it with a note about what it is and ask whether it changes the return. Don’t assume your CPA will find time to re-review the entire return.
Mistake 3: Leaving contractor 1099 data vague
If you paid a contractor $600 or more during the year, you must issue a Form 1099-NEC. Your CPA needs the contractor’s legal name, address, and tax ID (FEIN or SSN). Saying “I paid Bob for some work” is not enough. Get this information as you pay contractors throughout the year, not in September. Missing or incorrect 1099s trigger IRS penalties and file-compliance issues that ripple into future years.
Mistake 4: Not flagging unusual items yourself
If you loaned money to the business and want to claim it as a deduction, or if you had a one-time insurance claim or lawsuit settlement, flag it for your CPA upfront. These items often need special handling and tax treatment. Don’t bury them in a receipt dump and hope your CPA notices. A brief note—”I loaned the business $5,000 in June; is this deductible?”—takes 30 seconds and saves hours of back-and-forth.
A simple pre-deadline checklist you can send to your CPA
Two weeks before September 15, send your CPA an email with this message: “Hi [CPA name], here’s what I’ve organized for the 2026 return. Can you confirm you have everything you need to file by September 15, or should I get you anything else?”
- All 12 months of bank and credit card statements
- Business tax estimate payments made (if any)
- Quarterly payroll reports (if applicable)
- Sales tax returns filed (if applicable) and any exemption documentation
- Receipts and invoices for deductions claimed
- Contractor names, addresses, and tax IDs for 1099s
- A note on anything unusual or one-time that happened this year
This turns a stressful guessing game into a conversation. Your CPA either confirms they’re ready, or tells you exactly what’s missing so you can send it today.
Frequently Asked Questions
What if September 15 falls on a weekend or holiday?
The deadline is still observed as September 15. If that date falls on a weekend or federal holiday, the filing deadline typically shifts to the next business day. Confirm with your CPA what that means for your specific return. Don’t assume Monday morning is acceptable if September 15 is a Friday—email that day to be safe.
Can I ask for another extension after September 15?
No. September 15 is the final deadline for an extended return. If you miss it, the return is late, and penalties and interest apply. You cannot file another extension after the fact. This is why the checklist matters so much—there’s no second chance.
My CPA is slow to respond to my emails. What should I do?
Have a phone conversation in early August. Don’t rely on email for a deadline-driven task. Call, leave a voicemail, or text. Say you want to confirm all records are in hand and ask for their final submission deadline (not September 15 for them—earlier, so they have time to review and amend if needed). If they can’t commit to a timeline, find a new CPA before next year.
Do I need to sign the return before September 15?
Yes. Your CPA will prepare the return, but you must sign it. Many returns require an original ink signature or an electronic signature (e-signature) authorized by you. Plan for a signing appointment or e-signature workflow in early September. Some CPAs can prepare the return and send you a clean copy to review and sign electronically. Ask your CPA about their signing process in August.
What happens if I discover a mistake after I file?
You can file an amended return (Form 1040-X for individuals, Form 1120-X for corporations) at any time. An amendment doesn’t reopen the original filing deadline. If the amendment is in your favor, you’ll get a refund. If it shows you owe more, you’ll owe interest and possibly penalties on the original due date. The sooner you file (and file correctly), the fewer surprises you’ll face later.
This article is for general educational purposes and isn’t a substitute for advice from a licensed CPA or tax attorney. Rules vary by jurisdiction and change over time—always confirm current requirements with the Florida Department of Revenue or your advisor.
One habit to lock in now
September 15 doesn’t have to feel like a crisis if you build one habit: organize and send all tax records to your CPA by August 15, two months before the final deadline. This gives them time to ask questions, and you time to find what’s missing. If you’re managing multiple returns or dealing with sales tax in parallel, Outsourcing Processing can help you centralize and categorize transaction data so your CPA has one clean source of truth instead of hunting through folders. A little prep work now prevents a lot of stress in September.
If this kind of monthly work keeps slipping, see how business process outsourcing can take it off your plate for good.