Q3 Close: Books, K-1 Prep, And October Priorities

Updated: August 2026 · Industry Advisors · Education, not legal or tax advice.

September 30 is a quiet deadline that only feels quiet because nothing legally hard is due. In practice, it is one of the most consequential dates for a well-run LLC: the last chance to close Q3 books cleanly before October's insurance renewals, November's S-Corp election window, and December's year-end sprint start piling on. Founders who nail the Q3 close save eight-plus hours in April.

Here is the Q3 close checklist and the October handoff.

The Q3 Close · 8 Tasks By September 30

1 · Reconcile Every Bank And Card Account Through September 30

Every deposit matched to an invoice or funding source. Every withdrawal categorized to an expense account or transfer. Unresolved items go on a research list, not the trial balance.

2 · Run Year-To-Date P&L And Balance Sheet

Compare to Q3-of-last-year P&L. Note significant deltas — they'll matter for the S-Corp decision in November.

3 · Confirm All Q3 Estimated Tax Payments Posted

Match the September 15 confirmation numbers to the bank statement debits. Both federal and state. The Sept 15 deadline post covers the payment process; this step just verifies the money left the account.

4 · Post Depreciation For Q3

Any equipment purchases through September get depreciated per the elected method (Section 179, bonus, straight-line). Talk to your CPA before September 30 about accelerated methods for anything major bought this year.

5 · K-1 Preparation For Multi-Member LLCs

For multi-member LLCs (and S-Corps), K-1 preparation cascades from the reconciled books. Get the ownership ledger and distribution log to your preparer by mid-January. Q3 close data gives them enough to draft; year-end adjustments happen in January and early February. See the multi-member Operating Agreement clauses post for how ownership percentages should be documented.

6 · 1099 Contractor List

Pull the list of every contractor paid $600 or more year-to-date. Confirm each has a signed W-9 on file. Missing W-9s in October gives you two months to chase; missing them in January gets messy fast.

7 · Sales-Tax Nexus Check

Compare year-to-date revenue by state to economic-nexus thresholds. Any state where you have crossed the threshold needs registration in Q4. See the sales-tax nexus post.

8 · Update The Equity Ledger

Every capital contribution, distribution, and ownership transfer through September 30 recorded and reconciled with the bank statements.

October Handoff · What Starts Next

• Insurance renewals — pull declarations pages, shop the market, don't auto-renew
• Registered-agent and business-license renewals — confirm each state where you're registered
• Annual report filings — states with October/November deadlines (see the Q4 checklist for the state-by-state table)
• S-Corp election review — kick off the math in October; decide in November. Walk-through in the S-Corp election window post
• Retirement plan setup — Solo 401(k) must be established by December 31 for the current year

Common Q3 Close Mistakes

• Skipping the reconciliation because "the numbers look right." Six weeks later, they don't.
• Not confirming estimated-tax payments cleared. Sometimes ACH bounces. Sometimes payments apply to the wrong tax year. Verify.
• Forgetting sales-tax nexus checks. The threshold is measured on the prior year's activity in most states, so late Q3 is exactly when to check.
• Deferring the equity ledger until year-end. By December, you cannot reconstruct September's transfer terms accurately.

Where This Connects

Q3 close is the bridge between the Sept 15 payment (Sept 15 deadline post) and the year-end housekeeping sequence. The post-Sept 15 what's next post covers the broader quiet-quarter arc. Audit-defense hygiene from the audit triggers post starts at the Q3 close — clean quarterly reconciliation is the single most-cited factor in a smooth audit response.

Sources And Further Reading

• IRS · Business Taxes
• SBA · Manage Business Finances

The Everyday Owner's Blueprint maps the Q3 close, October renewals, November decisions, and December year-end onto one 12-month calendar.

Industry Advisors · 30 Wall Street, New York, NY 10005. Education, not legal or tax advice.