If your business filed a tax extension in March, July is the month to get serious about September. The extended deadline for S-corporation and partnership tax returns is September 15, and the financial records your CPA needs to complete that filing should be organized well before that call comes in.
For business owners who pay quarterly estimated taxes, September 15 carries a second obligation on the same date: the Q3 estimated payment for self-employed individuals, partners, and S-corp shareholders. One date, two deadlines. Summer tends to make both feel distant. They are not.
What The September 15 Deadline Actually Covers
S-corporations and partnerships that filed extension paperwork in March received an automatic six-month extension to submit their returns. The original deadline was March 16. September 15 is the hard stop, and no further extension is available after that date.
This applies specifically to businesses filing Form 1120-S (S-corporations) and Form 1065 (partnerships). Sole proprietors who filed individual extensions in April operate on a different timeline and have until October 15. If you own or co-own an S-corp or an active partnership, September 15 is your date.
One detail worth understanding clearly: the extension covered the time to file the return, not the time to pay any taxes owed. Any tax liability was due back in March. What September 15 brings is the completed filing, along with the Schedule K-1s that need to be issued to each shareholder and partner. If your CPA does not have accurate, reconciled financials from you before the window closes, that timeline gets compressed in ways that create problems for everyone involved.
What Your CPA Is Actually Looking For From You
When your accountant reaches out ahead of September 15, they need organized, reconciled financial statements. A profit and loss reflecting the business’s performance through at least the end of Q2, a balance sheet that matches actual account balances, and accurate documentation of any owner draws, distributions, or equity transactions that happened during the year.
If your books have not been actively maintained since spring, there is likely a meaningful gap between what the records show and where things actually stand. Uncategorized transactions, unreconciled bank accounts, and missing documentation all slow the filing process down. Every question your CPA has to ask takes time on both ends of the call, and the September 15 deadline does not move to accommodate a late-stage cleanup.
The more organized your financials when you hand them over, the faster and more accurately the return gets done.
The Q3 Estimated Tax Payment Due The Same Day
September 15 is also the Q3 estimated tax payment deadline for self-employed individuals, partners in a partnership, and shareholders in an S-corp who receive a share of business income. This payment covers income earned from June through August and is typically calculated using either 90% of the current year’s projected tax liability or 100% of the prior year’s tax (110% for higher-income filers).
The most common reason small business owners miscalculate or underpay Q3 estimated taxes has less to do with ignoring the deadline and more to do with working from an incomplete view of the year. If your books are behind by several months, you are projecting income on partial data. That is how underpayment penalties happen, and that is why the state of your records between now and September matters more than most owners realize in July.
Why Summer Is The Hardest Stretch To Stay Current On Books
July, August, and September are the months when bookkeeping most often falls behind. Owners are managing the daily demands of running a business, navigating seasonal shifts, traveling for work or taking needed time off, and making the hundred small decisions that don’t leave much room for month-end reconciliation. Closing the books in July feels like something that can wait until August. August feels the same way.
Then September arrives. Three months of uncategorized transactions, unreconciled accounts, and missing receipts sit in the queue, and an accountant is waiting on organized records with a hard filing deadline two weeks out. The time required to sort that backlog doesn’t compress to fit the schedule. It requires the same hours it always would have, compressed into a window that no longer has room for them.
This is also the stretch of the year when the cost of being behind becomes most visible, because the ask from the outside (your CPA, the IRS calendar) gets specific in a way it doesn’t in quieter months.
What To Do Before September Arrives
If your business filed an extension in March, contact your CPA now. Ask what they will need from you, what format they prefer to receive it in, and when they need it by to meet the September 15 deadline comfortably. Compare that list against the current state of your books. The sooner you understand the gap, the more time you have to close it.
If your records are current, this conversation takes about five minutes and gives everyone confidence heading into filing season. If the records are behind, July is a considerably better time to discover that than the third week of August. Pull bank and credit card statements for any unreconciled months, address uncategorized items in your accounting software, and document any owner transactions or equity activity that occurred in the first half of the year.
If the scope of what needs to be caught up feels like more than your schedule can accommodate, this is a reasonable moment to bring in professional support.
TEVA Supports Extended Filers Through Every Stage
At TEVA Bookkeeping Solutions, we work with S-corp and partnership owners who need their books in solid shape ahead of filing deadlines. Whether that means a midyear cleanup of Q1 and Q2 records or ongoing monthly bookkeeping through the fall, we work alongside your CPA so the financials they need are accurate and ready when they need them.
Contact us today to learn more about how we support small businesses through every deadline on the calendar.