The third-quarter estimated payment cleared on September 15, and the next fixed deadline is months away. That stretch is when year end tax planning pays off. Start now and every move is open; wait until December and the calendar makes half your decisions for you.

Why does year-end tax planning start in September?

The most valuable tax moves have lead times, and most of them expire on December 31. A retirement plan needs documents drafted, signed, and funded. Equipment has to be delivered and placed in service; paying for it is not enough. Deferring income or accelerating deductions needs a projection, and a projection needs books current through the third quarter. None of that happens in one December phone call.

September gives you three and a half months of runway, eight months of actual results to project from, and enough pay periods left to adjust withholding gradually. It is the right month to build a year-end tax planning checklist: each move that might apply, its deadline, and what has to happen first. After December 31, almost every lever locks. IRA contributions are one of the few exceptions, and they stay open until the April filing deadline.

Three tax moves that only work if you start before Q4

Three moves reward an early start more than any others. Each has a hard cut-off and takes weeks to do well.

The pattern is the same across all three: the deadline is December 31, but the work starts earlier. Plan documents take weeks. Equipment can sit in a supplier’s backlog, and a machine delivered January 4 deducts nothing for 2026. Reviewing losing positions in the fall lets you space sales instead of rushing December trades.

Should you defer income or accelerate deductions this year?

The answer comes down to one comparison: your expected tax bracket this year versus next. If 2027 looks like a lower-income year, deferring income and accelerating deductions shifts taxable income into the cheaper year. If your income is climbing, the reverse can make sense: bill sooner, hold deductible spending, and use this year’s lower bracket.

Cash-basis businesses have the most control, which is why this lever sits at the center of small business tax planning. A December invoice can go out in early January, and planned purchases can move up into this year. For high-income earners, tax saving strategies deserve a projection rather than a guess: bracket thresholds, the additional Medicare tax, and the alternative minimum tax can each change the math. Run the numbers before you commit.

How RRBB’s New Jersey advisors help with year-end tax planning

At RRBB, year-end planning is a year-round habit, not a December scramble. For 60+ years our RRBB advisors have worked with business owners and families across New Jersey, New York and Maryland from offices in Somerset and Union. As an independent member of PrimeGlobal, RRBB offers the expertise of a large firm while still serving clients with personal attention.

A fall planning conversation looks at the whole picture. Business tax planning and preparation covers projections, timing moves, and the January 15 estimated payment. Individual tax planning handles withholding, harvesting decisions, and charitable timing. Retirement and financial planning helps you choose and establish the right plan before the December 31 cut-off. If you run a business in Somerset, Union, or anywhere in central New Jersey, September is the month to get on the calendar.

When should I start year-end tax planning for my business?

September. That leaves eight months of results to project from, three and a half months to execute, and time to meet retirement-plan and equipment deadlines.

What tax moves have to be done before December 31?

Establishing most employer retirement plans, placing equipment in service, harvesting investment losses, making charitable gifts for a 2026 deduction, and nearly all timing moves. IRA contributions are the main exception; they stay open until the April filing deadline.

Should I defer income or accelerate deductions this year?

Defer income when you expect a lower bracket next year, and consider the reverse when your income is rising. Run a projection from your year-to-date numbers before you commit either way.

What is the deadline to set up a retirement plan for tax year 2026?

It depends on the plan. A solo 401(k) generally needs to exist by December 31, 2026, while a SEP can be set up as late as your 2026 filing deadline, including extensions. Ask your advisor which fits your payroll and headcount.

The runway only helps if you use it. Contact our RRBB advisors at (908) 231-1000 or through rrbb.com/contact to talk through your situation.