By the time most business owners think about taxes, the year is already closed and every option is off the table. The owners who pay less aren't luckier — they make three specific decisions in the third quarter, while the numbers can still move.
1. True up your estimated payments
If your income is running ahead of last year, your Q3 estimated payment (due September 15) is the last cheap chance to catch up. Underpay now and the IRS charges interest that compounds until April — currently one of the most expensive "loans" a business can take. Overpaying is no better: that's your working capital sitting interest-free with the Treasury.
2. Decide your retirement contribution — now, not in March
Solo 401(k)s, SEP-IRAs, and defined-benefit plans have different deadlines, but the contribution capacity is built by year-end payroll decisions. A business owner deferring the maximum can shelter tens of thousands of dollars per year — but only if compensation and plan elections are set before December, which means deciding in Q3.
3. Time your equipment purchases deliberately
Section 179 and bonus depreciation can make a year-end equipment purchase dramatically cheaper after tax — but only in a year when your income is high enough to absorb the deduction. Buying in a low-income year wastes it. Q3 is when your CPA can project the year accurately enough to tell you: buy in December, or wait until January.
The common thread
All three moves share one requirement: current books and a projection. If your bookkeeping runs months behind, you can't make any of these decisions in time. That — more than any single deduction — is why integrated bookkeeping and tax planning saves money.