September Is When Your Tax Year Gets Decided
September shows up on the calendar and most high earners do the same thing: they glance at it, file it under "later," and keep running the business.
I see the pattern every fall. An executive with a big vest still ahead. An owner who might sell next year "if the right buyer shows up." A household staring at a deferred-comp election form they haven't opened. Everyone agrees taxes matter. Almost nobody puts a date on the calendar that isn't December.
December is when taxes feel real. That's when the CPA emails, the estimated payment reminders hit, and everyone suddenly wants a strategy.
Here's the problem.
By December, a lot of the decisions that actually move your tax bill are already closed. Not "hard." Closed. Election windows shut. Vesting already happened. Charitable gifts that needed paperwork months ago are now a scramble. Conversion opportunities that only work in a lower-income stretch are gone because the year filled up with salary, bonus, and equity income.
September is when the tax year gets decided. December is when you find out what you decided by default.
I'm not talking about clever loopholes. I'm talking about timing — the boring, rules-based kind that separates intentional outcomes from accidental ones. Feelings say "I'll deal with it when it's urgent." Rules say "deal with it while you still have options."
What "tax timing" actually means
For a W-2 executive or business owner, your tax year isn't one number. It's a stack:
Base salary and bonus
Equity income (RSUs at vest, ISO exercises, option sales)
Investment income and K-1s
Deferred compensation elections and distributions
Charitable gifts and estimated payments
Sometimes a conversion, a sale, or a liquidity event
Each of those has a clock. Some clocks are soft. Some are hard. September is when you still have enough runway to coordinate them on purpose.
December is when you're negotiating with a year that's mostly already written.
The five clocks that matter before Q4 hardens
1) Equity events you can still shape
RSUs that already vested are income. You can't unwind them. What you can still shape for many executives is what happens next: whether you sell on a schedule, hold past a concentration threshold, or wait for a trading window that collides with year-end estimated payments.
The tax bill isn't only "what vested." It's also when you recognize gains on shares you sell, how withholding compares to your all-in rate, and whether December liquidity is forced by a tax bill you didn't size in September.
If you own too much of one company, waiting until December to "think about selling" is feelings, not a plan. A rules-based sell-down doesn't need a crystal ball. It needs a calendar.
2) NQDC and other irreversible elections
If your company runs a nonqualified deferred compensation plan, the election window often sits in the fall — sometimes earlier than people expect. Miss it and you're usually locked out for the next year's compensation. Max it without a distribution design and you can build a future tax mountain.
This isn't a deep dive on NQDC (we've covered the traps before). It's a timing point: the form that shows up in your inbox in September or October is not a "deal with it in December" item. Once you sign, you generally can't unwind it because December felt busy.
3) Estimated payments and the underpayment trap
High earners with lumpy equity income often underpay during the year and overcorrect in April — or get surprised by underpayment penalties because withholding never matched the stack.
September is a clean checkpoint: project the full year (salary + bonus + equity + other income), compare deposits to date, and decide whether a Q3/Q4 estimated payment closes the gap before April becomes expensive theater.
The goal isn't perfection. The goal is intentional deposits that match an intentional year.
4) Charitable giving that needs paperwork, not vibes
Donor-advised funds, appreciated stock gifts, and bunching strategies work best when the shares, the documentation, and the account are ready before the December crush. Waiting until the last week of the year turns a clean move into a scramble — and sometimes into a miss.
If giving is part of your plan, September is when you decide what and from which account, not whether you "feel generous" in December.
5) Opportunistic windows: conversions, harvesting, residency, and deal prep
Roth conversions, tax-loss harvesting, state residency timing, and pre-exit structuring all share one trait: they work better in years (or months) you choose on purpose.
A peak RSU year is often a terrible year to force a conversion "because everyone says Roths are good." A lighter income stretch, a job transition, or a planned lower-bonus year can be a better window — but only if you spot it before the year fills up.
Same idea for owners eyeing a sale: the eighteen-month runway doesn't start when the LOI arrives. If a 2027 or 2028 exit is even plausible, September planning is early enough to matter and late enough to feel real.
One more quiet September job: align the people. Your CPA, wealth advisor, and (when needed) attorney should be looking at the same year-type sentence and the same deadline page. Tax prep without coordination is how good households still leave timing on the table.
A September framework (rules over feelings)
Use this as a working session with your CPA and advisors — not as personalized advice, and not as a mandate to do any one move.
Step 1 — Name the year type
Is this a peak year, a normal year, or a dip year once you include equity?
Write one sentence: "2026 is a ___ year because ___."
If you can't finish that sentence, you're flying blind into Q4.
Step 2 — List the hard deadlines
On one page:
NQDC / equity plan election windows
Trading windows and blackout periods
Estimated payment due dates
Charitable paperwork lead times
Any trust, gift, or entity filings already in motion
Hard deadlines get dates. Soft intentions get cut.
Step 3 — Pressure-test withholding vs. reality
What will be withheld from wages and equity vs. what your all-in rate implies?
If there's a gap, choose the gap-closer now (extra withholding, estimated payment, or a planned sale for liquidity) — not after the surprise bill.
Step 4 — Separate "tax tail" from "risk dog"
Concentration risk doesn't wait for a favorable tax year. If one company is too much of your net worth, the rule is diversification on a schedule. Taxes inform how you execute. They shouldn't veto the rule.
Step 5 — Pick two moves, not twelve
September planning fails when it becomes a fantasy checklist. Pick the two timing decisions that change the most for this year and execute those. Park the rest for a dated follow-up.
Signal over noise
The noise says: "We'll figure out taxes in December."
The signal says: December is a reconciliation month. September is a decision month.
Rules over feelings means you don't wait for the bill to feel urgent before you look at the clocks that already started ticking.
If you want to pressure-test a piece of this before Q4 hardens, we built a few free tools for that.
RSUs, ISOs, NSOs: run the stack, not just the vest. https://forecastcapitalmanagement.kit.com/exec-comp-opt
NQDC elections: defer vs. take it, with the clocks attached. https://forecastcapitalmanagement.kit.com/nqdc
Owners weighing a sale: whether selling actually makes you wealthier over the long run. https://sellsmartplanner.com
If you’d rather walk the September framework with a second set of eyes, reply or reach out. Educational pass first.
Wealth Built on Vision, Secured by Strategy.
This is for educational purposes only and is not investment, tax, or legal advice. It is not a recommendation to buy, sell, or hold any security. Consult your own advisors before acting.
