If you filed an extension back in March, this is what your CPA needs from you before it runs out.
An extension buys time, but it doesn't buy forgiveness. If you're an S-Corp, LLC, or partnership that filed Form 7004 back in March, your extended deadline is September 15. Missing it doesn't just mean a late filing, penalties get calculated back to the original March due date. The extension moved your deadline. It didn't reset the clock the IRS is watching.
Here's what to have ready.
Reconciled Books Through Year-End
This is the foundation everything else in your return depends on. Every account matched, every transaction categorized, no gaps. If your bookkeeper hasn't confirmed reconciliation is complete, that's the first call to make this week, not the 14th.
What S-Corps Need
Officer compensation needs to be documented as reasonable, since the IRS can and does scrutinize S-Corp officer pay that looks artificially low relative to the work performed. If you took distributions instead of a salary, or your salary looks thin compared to what the role would normally pay, talk to your CPA about it now.
K-1s go out to shareholders on Form 1120-S alongside the filing itself, not after. If any loans passed between you and the business this year, they need to be documented as loans on the books, not left as an unexplained transaction your CPA has to reconstruct.
What Partnerships Need
Schedule K-1s are due to partners on the same timeline as Form 1065. If profits or losses were allocated differently than ownership percentage this year, called a special allocation, that needs to be documented and justified before filing, not explained after the fact if the IRS asks.
What Multi-Member LLCs Need
If your LLC is taxed as a partnership, the same K-1 deadline applies. The detail that trips people up most: your operating agreement is supposed to reflect how profits actually got distributed. If those drifted apart during the year, that gap needs to be addressed with your CPA before filing.
Documentation, Regardless of Entity Type
Backup for expenses. Receipts, bills, and documentation for anything claimed as a deduction.
Large expense documentation. Anything your CPA needs to depreciate, including vehicle purchases broken out separately into the fixed asset and expense portions.
Inventory detail, if applicable. Beginning and ending inventory totals, purchases, and any items removed for personal use.
Asset purchases or sales. Documentation for anything bought or sold that needs to be recorded on the return.
Adjusting journal entries. Confirm anything your CPA sent earlier in the year has actually been entered into your books.
Mileage logs. Required for any business vehicle use you're deducting.
Payroll tax returns and W-2s/1099s. These should already be filed, but your CPA will want copies on hand for cross-reference.
Loan interest documents. End-of-year balance and interest paid, for any business loans.
End-of-year bank and credit card statements. Full year, not just the months your bookkeeper flagged as unclear.
Unreported Income
Cash payments, barter transactions, or anything that didn't run through your normal books still needs to be reported. This is the category most likely to get missed, and the one most likely to cause problems later if it's found instead of disclosed.
What Happens If You Miss It
Filing late after an extension typically triggers a penalty of 5% of unpaid tax per month, capped at 25%, calculated from the original deadline in March, not from September 15. The exact numbers depend on your specific situation, so confirm directly with your CPA if you're at risk of missing the date, but the short version is that the extension only helped if you actually file by the date it bought you.
We covered the original March deadline and what it required in more detail in our first tax prep checklist, most of what applies there applies here too, just with September numbers instead of March ones.
Frequently Asked Questions
What happens if I miss the September 15 extended deadline?
Penalties apply retroactively to the original March filing deadline, not to September 15. The longer the delay, the larger the penalty, up to a cap. Contact your CPA immediately if you're going to miss the date, options exist but they narrow the longer you wait.
Do I still need to pay taxes owed by September 15, or just file?
The extension applies to filing the return, not to paying any tax owed. If you owe money and didn't pay an estimate back in March, interest has likely been accruing since the original deadline regardless of the extension.
What's the difference between what my CPA needs and what my bookkeeper handles?
Your bookkeeper's job is making sure your books are reconciled and current. Your CPA uses those books to prepare and file the actual return. If your books aren't current, your CPA is working from incomplete information, which slows the filing down and often increases their fees.
If any of this feels like more than you were expecting to pull together this week, that's usually a sign your books weren't as current as they needed to be. MH Consulting + Bookkeeping works with S-Corps, LLCs, partnerships, sole proprietors and individuals across the Bay Area and nationally, we're happy to help you get ready before the 15th.