End of Quarter Bookkeeping Checklist for Small Business (Q3)
An end of quarter bookkeeping checklist for a small business comes down to six moves: deposit every check, pay the bills you’d pay next week anyway, tie payroll to the ledger, count inventory, write down owner draws, and then build the fourth-quarter estimate from three real quarters. The third quarter ends Wednesday, September 30. Everything on this list is easier to do in the next three days than in the three weeks after.
We run an accounting firm, and the quarter-end is where a good monthly close pays for itself. If the books are closed through August, Q3 is one more month and a short list. If they aren’t, this is the list that keeps October from becoming a scramble.
Deposits and bills
On cash-basis books, which is most small businesses, revenue counts when the money hits the bank and expenses count when they leave it. That makes the last three days of the quarter a lever.
Deposit every check in the drawer by Wednesday. A check that sits until Friday moves that revenue into Q4. That’s fine if it’s intentional. It’s a problem if it isn’t, because your Q3 profit, your estimate, and your year-to-date margin will all be understated by checks you already have.
Pay the bills you’d pay next week anyway. Same logic in reverse. If the vendor bill is due October 5 and the cash is there, paying it September 30 puts the expense in Q3 where the revenue it supported already sits. This isn’t tax planning so much as making the quarter describe itself honestly. The estimate you build next week will be based on it.
Invoice everything that’s finished. Every job completed in September should have an invoice dated September, even if it won’t be paid until October. On cash-basis books it doesn’t change Q3 revenue, but it starts the collection clock and it makes the receivables list real for the cash forecast.
When is the Q3 941 due?
Form 941 for the third quarter covers July through September wages and is normally due October 31. This year October 31 falls on a Saturday, so the due date moves to Monday, November 2, 2026. Don’t plan around the extra two days; plan around what has to be true before it’s filed.
The wages, withholding, and employer taxes on the 941 must match the ledger. Not approximately. To the dollar. Here’s the tie-out:
- Gross wages on the payroll reports for July, August, and September equal wages expense in the books for those months.
- Employer payroll taxes on the reports equal payroll tax expense.
- Every tax deposit made during the quarter is booked against the payroll liability, so the liability balance at September 30 is only what’s still owed.
- Any payroll-provider fees are in their own expense account, not lumped into wages.
The reason this matters beyond the 941: the four quarterly 941s have to add up to the W-2s you’ll issue by January 31, 2027, and the W-2 total has to match wages on the tax return. The IRS reconciles all three. If the books say one thing and the filings say another, the notice arrives months later, and the fix is a corrected return. Tying it out now, one quarter at a time, is the only way to avoid that.
Inventory
If you sell product, count it once a quarter at minimum. Wednesday evening after close is ideal.
Without a count, cost of goods sold is whatever you paid vendors that quarter, which is purchases, not cost of sales. A restaurant that stocked up in late September for a busy October will show a terrible Q3 food cost and a wonderful Q4 one, and neither number is true. A retailer who bought holiday inventory in September has the same problem larger. One count separates real margin from made-up margin, and it’s the difference between a Q3 profit you can build an estimate on and one you can’t.
The count doesn’t need to be perfect. It needs to be consistent, done the same way at the same point every quarter, so the trend is real even if any single number is a little off.
Owner draws
Write them down now. Every transfer to your personal account, every personal charge on the business card, every “I’ll pay that back” from July. Nobody remembers July in October, and nobody remembers October in February when the preparer asks.
Draws matter at quarter-end for two reasons. They aren’t expenses, so if they’re sitting in Auto or Meals or Miscellaneous, your profit is understated and your estimate will be too low. And for S-corp owners, the split between salary and distributions is a year-end question that’s much easier to manage with a quarter left than with a week left. If distributions are running far ahead of salary, the fourth quarter is when to correct it through payroll.
How do I prepare for quarterly estimated taxes?
The next individual estimate is the fourth-quarter payment, due January 15, 2027. It’s the last one for 2026, and the one most worth getting right, because it’s the last chance to avoid an April surprise or a large overpayment.
With three closed quarters, the estimate stops being a guess. Take actual year-to-date profit through September 30, add a fourth-quarter projection based on what you know is coming, run the total through the tax at your rates, subtract what’s already been paid in the first three estimates and through withholding, and what’s left is the January payment. For calendar-year C corporations, the same logic applies to the fourth installment due December 15, 2026.
Compare that to the safe-harbor approach, which pays a fraction of last year’s tax and hopes. If this year is better than last year, safe harbor leaves a balance due in April. If it’s worse, you’ve loaned the IRS money for a year. A real estimate from real quarters is usually the biggest cash decision of the season, in one direction or the other.
What a CFO does with this number
A fractional CFO uses quarter-end as the checkpoint. Three closed quarters plus a projection is enough to see the whole year, and the fourth quarter is the last one with time to change it.
The estimate is the first thing. The second is the fourth-quarter plan: whether to buy the equipment now (100% bonus depreciation and Section 179 both apply to qualifying property acquired and placed in service this year, so a December purchase changes the number), whether to run a bonus through payroll, whether the S-corp salary needs adjusting before December 31, and what the cash forecast says about all of it. Every one of those decisions depends on Q3 being closed and true, which is why the checklist above isn’t housekeeping. It’s the input.
Where we come in
For our clients, quarter-end isn’t a separate project. It’s the September close: deposits and bills handled in the normal rhythm, payroll tied out every pay date because we run it in-house, inventory counts scheduled, draws booked as draws all year. The 941 is filed from books that already match it. The Q4 estimate is built in October from three closed quarters, with time to talk about it.
If your quarter ends Wednesday and none of this is done, reach out. We’ll start with a two-hour diagnostic, get Q3 closed properly, and build the January estimate from real numbers.
Frequently asked questions
What should I do in the last days of the quarter?
Deposit every check, pay bills you’d pay next week anyway, tie payroll reports to the ledger, count inventory, and write down owner draws.
When is the Q3 Form 941 due?
Normally October 31, but because October 31, 2026 is a Saturday, the due date is Monday, November 2, 2026. The wages on it must match the books and the W-2s you’ll issue in January.
How is the Q4 estimate built?
From three closed quarters plus a fourth-quarter projection, run through the tax, minus what’s already paid.
