It's 10PM, Do You Know your Marginal Rate? How to Make Better Tax Decisions

It's 10:04 on a Tuesday night in November. The benefits enrollment is due by midnight. The deferred compensation election is still sitting in a browser tab and in your fatigued state you are not confident about this decision.

The form simply requests what percentage of next year's salary and bonus you want to defer. And it wants a payout election. Lump sum at separation, or installments over five, ten, or fifteen years.

The monologue running through your head might sound like this…

“The RSU vesting in February puts me in the top bracket again, so deferral is the right move. But expenses next year are high with the kitchen renovations, so I might need the cash flow. Oh, but I can sell the vested stock, but then am I paying more taxes, and what if the stock is down? How long will I really be working here anyway?”

It's murky at best, so you pick what you picked last year which is what your colleague two offices down said she did. You close the laptop.

That decision, made without the needed context and data, might be a six-figure unforced error.

I'm using deferred comp benefits to illustrate, but similar complex high impact decisions are made on loose assumptions. It could be an option exercise, an RSU sale, a pension election, or even how you structure selling a business. In the current investment environment, especially if retirement is within a few years, you need tools to make these decisions with confidence.

By far the most illuminating reference for big decisions like this is a pro-forma cash flow. Think of a personalized spreadsheet that projects how much money you need, when you need it, and where it is going to come from. A cash flow projection is like a pair of Sketchers or a colonoscopy, everyone “of a certain age” should have one.

You can learn more about that here, but this article describes another handy tool you will need for benefits enrollment or many other decisions— your Personal Tax Profile.

To Defer or Not

For high income professionals, most benefit decisions come down to paying taxes now or later. Roth or traditional. Defer the comp or take the income now. Backdoor conversion or skip it. Sell the position or hold it another year. What basic inputs do you need to make such a decision? You need to be able to do the math to compare pay now versus pay later, which means you need to know your current tax rates and have reasonable expectations about your future personal tax rates. That's what a personal tax profile would provide.

If you had one, you might see how a benefit decision that defers paying taxes at 37% today into a likely future rate of 24% makes sense. Or you might see how that lump sum choice you just made is going to defer your current 32% rate in favor of a 37% rate the year you retire.

The question underneath the question

You need a time horizon for the estimate of future tax rates, and the pro-forma cash flow is the robust way to make the estimate. But for simplicity, just consider when you will be forced to the taxable event — a deferred comp distribution — or when you will need to generate taxable flows from retirement accounts or appreciated assets. Add Social Security and other sources of income and you start to see what your taxable income future looks like at different stages. There is rich opportunity for tax planning here, but I am emphasizing simplicity for now.

This is far more critical at 55 versus 40. With five or even ten years to the exit, the payout year is close enough to see and the projection can be reliable. Now let's see what goes on the Personal Tax Profile.

Past, Present, Future and the Reservoir

One piece of housekeeping first, because this trips up more people than it should. Your marginal rate is the rate on your next dollar determined by what bracket you sit in. Your effective rate is what you actually paid across everything. Marginal is the decision variable. Effective is the scorecard. They get used interchangeably, and then the math stops working.

Personal taxes get complicated in a hurry, but the decisions in front of you turn on a fairly small set of numbers: what you paid, what you are paying now, and what you expect to pay later. A surprising number cannot name the bracket they are in. The profile fixes that. It covers four periods and one standing balance.

Last year, as filed. Your baseline, and the easiest section to build, because every number is already sitting on your return. Total household income, then what you actually paid, separated into federal income tax, payroll tax, capital gains tax, state tax and property tax. Add them up. That total is a number most people have never seen in one place, and it tends to land higher than the one they have been carrying around. Building it also has a way of surfacing filing mistakes and missed opportunities from a year you can still amend.

This year, projected. The only period you can still do something about. Start with expected income for the year, split between ordinary and qualified, then run out the rates. If the year looks a lot like last year, last year's return is a fine guide. The line that earns its keep here is the room left between your current bracket and the next one, because that number tells you how much additional income you can recognize before it gets expensive.

Next year, projected. When you defer income or an asset sale into next year, next year's rate is the rate you are buying. Most people making that trade have never looked at it.

The named planning year. Pick the year that matters to the decision in front of you: the deferred comp payout, the business sale, the year RMDs begin. Project income by source, then the rates that follow from it. This is the column that answers the question you actually have, and it is the one that needs the personalized pro-forma cash flow behind it.

The reservoir. Capital loss carryforwards. Suspended passive losses. Charitable carryforwards. Cost basis by lot. These are dollars already banked against a future bill. They do not belong to any single year, which is precisely why they get forgotten.

Assembled, a tax profile might look like this:

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Notice the marginal bracket in this case is projected to drop from 37% to 24% with over $162K of marginal income before bumping into the next bracket. That’s the kind of revelation that leads to better financial decisions.

Three ways this earns its keep:

You have been sitting on a stock you won't sell. You priced the sale in your head at the top rate. But there is $184,000 of capital loss carryforward from an old bad year that you forgot existed, and gains stack on top of ordinary income rather than replacing it. The real bill on trimming that position is a fraction of the imagined one.

You are wondering whether this is a Roth conversion year. The profile gives you the variables needed to decide. Almost no room this year, $162,600 of room in the first retired year.

And the 10:04 election. With the profile open, the lump sum and the ten-year installment decision is now informed by two rates, side by side, with your projected income in that year sitting underneath them.

Pulling it Together

Most of the data needed for your Personal Tax Profile is on the returns you have already filed, and if you are a do-it-yourself planner, using AI tools carefully can produce reasonable estimates of future rates for your situation.

The pro-forma cash flow projection is the planning gold standard that anyone within a few years of retirement ought to have anyway. But that takes a substantial time commitment and some familiarity with retirement income planning. If you have neither, that is a perfectly reasonable thing to hand to an advisor or planner.

What matters is that you stop making six-figure decisions on a tax rate you have never actually calculated.

This article is for educational purposes only. It should not be considered financial advice or tax advice related to your particular situation. Tax rules, plan terms, and thresholds vary and change. Consult a professional advisor before taking any action related to the content of this article.