Tax Gross Up: What It Is and How to Calculate It

The first time I promised a candidate a $5,000 signing bonus, I meant $5,000. What arrived in her account was closer to $3,500. She was too polite to say anything for about a week, and then she asked, carefully, whether there had been a mistake.

There had not been a mistake. There had been a misunderstanding, and it was mine. A bonus is supplemental wages. It gets withheld on like any other wage: 22 percent federal, 7.65 percent FICA, plus whatever the state takes. I had quoted a gross figure and described it as a net one, and the gap between the two was about $1,500 of goodwill I did not need to lose in someone's second week.

The fix is a gross-up, and the math takes about ninety seconds once you know which direction to run it. This guide covers what a tax gross-up is, the formula, worked examples for bonuses and relocation, the IRS rules that govern it, the four calculation methods and which one you actually need, what a gross-up really costs you once employer taxes are in, and the cases where the right answer is not to gross up at all.

What Is a Tax Gross-Up?

A tax gross-up is additional gross pay an employer adds to a payment so that the employee receives a specific net amount after taxes are withheld. It reverses the normal direction of payroll. Instead of starting with a gross wage and subtracting taxes to find net pay, you start with the net pay you promised and solve backward for the gross wage that produces it.

The mechanics matter because a lot of small business owners think of a gross-up as the employer paying the tax on the employee's behalf. That is not quite what happens. You are not paying someone else's tax bill. You are paying a larger wage, and the larger wage generates enough withholding to leave the promised net behind. The employee's W-2 shows the bigger number. The tax was withheld from their wages in the ordinary way. You just made the wages bigger to compensate.

That distinction has practical consequences, and I will come back to them: the grossed-up amount is real, reportable income to the employee, it appears on the W-2, and it increases what you owe in employer payroll taxes. The gross pay vs net pay guide covers the underlying relationship in more detail.

What Grossed Up Means on a Paycheck

When a payment is described as grossed up, it means the gross figure on the pay stub was calculated in reverse from a target net. The employee sees a larger gross wage and a correspondingly larger withholding line, and the two cancel out to the number they were promised.

You will occasionally see the phrase used in a completely different context. In finance, a dividend can be grossed up for tax credits, and mortgage underwriters gross up nontaxable income to compare it against taxable income. Loan and acquisition agreements contain gross-up clauses. None of that is what a payroll gross-up refers to. In an employment context, grossed up almost always means the payroll calculation described here.

The confusion is worth heading off because employees search the term after seeing it on a pay stub or in an offer letter, and the finance meaning is the first thing many of them find. If you use a gross-up, explain it in writing when you make the offer.

When Employers Gross Up Pay

Employers gross up when a payment has been communicated as a net figure and the business has decided to honor that figure rather than let withholding erode it. Six situations account for nearly all gross-ups at companies with 5 to 50 employees.

The pattern across all six: the payment is supplemental wages, the employee was told a number, and that number was the net. Regular salary is almost never grossed up, because nobody quotes a salary as take-home. The exception is net-salary agreements, which are rare below the executive level and create a permanent administrative burden. The bonus guide covers how bonuses get taxed in the first place, and the severance package guide covers the separation case.

The Gross-Up Formula

The gross-up formula is desired net divided by (1 minus the total tax rate). Everything else is a matter of correctly identifying which taxes apply and at what rate.

The federal supplemental rate is fixed at 22 percent for supplemental wages up to $1 million per employee per calendar year. Above that cumulative threshold, the excess is withheld at 37 percent, and that rate is mandatory. Per IRS Publication 15, both rates were made permanent by P.L. 119-21, so there is no sunset date to plan around. For a business with 5 to 50 employees, the $1 million threshold is unlikely to come up, but it exists.

FICA is 7.65 percent of wages: 6.2 percent for Social Security up to the annual wage base, and 1.45 percent for Medicare with no cap. That gives you a federal floor of 29.65 percent before a single dollar of state tax enters the calculation. The FICA tax guide breaks down both components.

State supplemental rates are where this gets local. Some states have no income tax and drop out of the equation entirely. Others impose a flat supplemental rate. A few require you to use regular withholding tables even for supplemental payments. Look up your state before you calculate, and use the illustrative 5 percent rate in the examples below only as a placeholder.

Worked Example: A $5,000 Signing Bonus

Here is the full calculation for the situation I described at the top of this article. The candidate was promised $5,000 in her pocket. The company is in a state with a 5 percent supplemental rate, so the combined rate is 34.65 percent.

Two things jump out. The first is that $5,000 net required $7,651.11 in gross wages, which is 53 percent more than the promised figure. The second is that the true cost, once the employer share of FICA is added, was $8,236.42. If you budgeted $5,000 for that bonus, you are 65 percent over.

Run the same bonus in a state with no income tax and the combined rate drops to 29.65 percent. The grossed-up wage becomes $7,107.32 and the loaded cost becomes $7,651.03. The state rate is the single biggest lever in the entire calculation, and it is the one most people forget to look up.

State rates are illustrative. Confirm your own state supplemental rate, because it moves the final number more than any other input.

Why the Tax on the Tax Matters

The reason you divide rather than multiply is that the gross-up is itself taxable wages. Add money to cover the tax, and the added money gets taxed too. Multiplying the net by the tax rate and adding it on top ignores this entirely, and the employee ends up short.

Take the $5,000 bonus at a 29.65 percent combined rate. The intuitive approach is to calculate 29.65 percent of $5,000, which is $1,482.50, and add it: $6,482.50 in gross wages. Run that through payroll and withholding takes 29.65 percent of $6,482.50, which is $1,922.06. The employee nets $4,560.44. You are $439.56 short of the promise, and you already paid an extra $1,482.50 to get there.

Division solves this in a single step because it asks a different question. Rather than "how much tax will be owed on $5,000?" it asks "what gross amount, after losing 29.65 percent of itself, leaves $5,000 behind?" That is what dividing by 0.7035 answers. It is an inverse operation, which is why the correct approaches are all called inverse methods.

The Four Calculation Methods

There are four ways to calculate a gross-up, and one of them is wrong. The other three differ in how precisely they estimate the tax rate that will actually apply to the payment.

For a business with 5 to 50 employees, the supplemental inverse method covers nearly every case. Use it for signing bonuses, spot bonuses, relocation, and taxable allowances. Reach for the marginal inverse method only when the payment is large enough that the difference between the 22 percent flat rate and the employee's real marginal rate translates into real money, which usually means five figures or an executive agreement.

The aggregate method is not really optional in one specific case. Per IRS Publication 15, if you did not withhold income tax from the employee's regular wages in the current or immediately preceding calendar year, you cannot use the flat 22 percent rate and must aggregate. This is an edge case, but it exists.

Relocation Gross-Ups and the Permanent Moving Expense Change

Employer-paid or reimbursed moving expenses are taxable W-2 wages for almost every employee, and that treatment is now permanent. This is the single most commonly misunderstood fact in relocation, and it directly drives the need for a gross-up.

Before 2018, qualified moving expense reimbursements were excluded from an employee's income. The Tax Cuts and Jobs Act suspended that exclusion, and the suspension was originally scheduled to expire after 2025. It did not. P.L. 119-21 permanently repealed both the moving expense deduction and the employer reimbursement exclusion. Per IRS Publication 15-B, the exclusion for qualified moving expense reimbursements is permanently eliminated. It does not revert.

The exceptions are narrow. Active-duty members of the Armed Forces moving under a permanent change of station retain the exclusion, and P.L. 119-21 extended it to certain intelligence community employees and new appointees for moves in 2026 or later. IRS Topic No. 455 covers the details. Unless you are hiring from one of those two populations, the exceptions do not apply to you.

The practical consequence: if you reimburse a new hire $8,000 for their move and do not gross it up, they receive roughly $5,200 after withholding and pay the remaining $2,800 of their moving costs out of pocket. Grossing that $8,000 up to a true net at a 34.65 percent combined rate requires $12,241.78 in gross wages and costs you $13,178.28 loaded. Relocation is expensive. Discovering it is expensive after you promised a number is worse.

IRS Rules You Need to Know

Three IRS rules govern how a gross-up gets withheld and reported. Get these wrong and the calculation is academic.

Supplemental Wages Have Their Own Withholding Rate

Bonuses, commissions, severance, back pay, retroactive raises, taxable fringe benefits, and moving expense payments are all supplemental wages. Per IRS Publication 15, when supplemental wages are identified separately from regular wages, you may withhold federal income tax at a flat 22 percent, and no other percentage is permitted. You cannot withhold 25 percent because it feels safer or 15 percent because the employee asked. It is 22 percent or you use the aggregate method.

The $1 Million Threshold Is Cumulative and Mandatory

Once an employee's cumulative supplemental wages for the calendar year exceed $1 million, the excess is withheld at 37 percent, and the mandatory rate applies regardless of the employee's Form W-4. Only the amount over $1 million is subject to the 37 percent rate. This is a threshold most small businesses will never reach, but it is worth knowing that it exists and that it is not elective.

Grossed-Up Wages Are Reported as Wages

The grossed-up gross figure flows into Boxes 1, 3, and 5 of the W-2. This is not a footnote. It means the employee's reported income is meaningfully higher than the cash they received, and it means gross-up arrangements are permanently visible in your payroll records. The payroll forms guide covers what gets reported where.

How FICA Changes the Math

FICA sits inside the gross-up divisor and outside it at the same time, and this trips people up. The employee's 7.65 percent share is withheld from the grossed-up wage, so it belongs in the divisor. Your matching 7.65 percent is an additional employer cost calculated on top of the grossed-up wage, so it does not belong in the divisor and does belong in your budget.

Two wrinkles change the divisor in specific cases. Social Security stops at the annual wage base. If an employee has already crossed it, the 6.2 percent drops out of their withholding for the rest of the year, and your divisor should reflect that or you will over-gross the payment. For 2026 the wage base is $184,500, per the Social Security Administration.

Going the other way, the additional Medicare tax adds 0.9 percent to employee withholding on wages above $200,000. There is no employer match on that 0.9 percent. If a bonus pushes someone across that line, the employee's effective rate rises and the divisor shrinks. For most companies in the 5 to 50 employee range neither wrinkle applies often, but both are worth a check before you gross up a large payment for a highly compensated employee. The Medicare tax guide covers the thresholds.

What a Gross-Up Really Costs

A grossed-up payment costs roughly 40 to 65 percent more than the net figure you promised, and the range depends almost entirely on your state. That is the number to budget against, not the net.

Build the cost in three layers. The first layer is the grossed-up wage itself. The second is the employer share of FICA, at 7.65 percent of the grossed-up wage. The third is unemployment tax: FUTA plus your state unemployment insurance rate, applied to the grossed-up wage until the employee crosses the relevant wage bases. That third layer is small for most established employees who cross the FUTA and SUTA wage bases early in the year, but it is not zero for a new hire receiving a signing bonus in their first pay period.

The precedent problem is the one that surprises founders. A gross-up is a discretionary act of generosity the first time you do it. By the third time, it is policy, whether or not you wrote it down. Decide in advance which payments get grossed up and put it in writing before anyone has to ask why they were treated differently. The total compensation guide covers how to structure this so it holds together across a growing team.

When You Should Not Gross Up

The right answer is sometimes not to gross up. Four situations where I would advise against it.

When the Cost Is Not Budgeted

If you promised $5,000 and budgeted $5,000, you cannot afford the gross-up. The honest move is to quote the gross figure and tell the candidate what to expect after withholding. A candidate who receives $3,517 they were expecting is fine. A candidate who receives $3,517 they thought would be $5,000 is not.

When It Creates a Pay-Equity Problem

Grossing up one relocation package and not another, or grossing up a bonus for one hire and not their peer, produces differences in total compensation that are recorded on W-2s and eventually discussed in break rooms. If you cannot articulate a defensible reason for the difference, the difference is a liability. The pay equity guide covers what makes a compensation distinction defensible.

When It Sets a Precedent You Cannot Sustain

The first grossed-up relocation is a competitive advantage. The fifth is a line item you cannot remove without a fight. Ask whether you would still gross up if you were doing it for every hire at your projected headcount in eighteen months. If the answer is no, do not start.

When a Different Structure Solves the Problem Better

Sometimes the underlying goal is not "the employee should net $X" but "the employee should not be out of pocket for a business expense." If that is the case, an accountable expense reimbursement plan may achieve the goal without creating taxable wages at all. Reimbursements under an accountable plan, with substantiation and return of excess amounts, are generally not wages. That does not work for moving expenses anymore, but it works for a range of other business costs. The HR processes guide covers where reimbursement policy belongs in your workflow.

Handling Gross-Ups in Your Payroll and HR Workflow

The calculation is the easy part. The failure mode at small companies is never bad math. It is that the gross-up did not get entered before the payroll run closed, or the promised net was in an email nobody could find when it came time to pay it.

Most of these steps fail for the same reason: the promise is made in one system and executed in another, and nothing connects them. I built FirstHR around this gap. Offer terms captured with e-signature at the offer stage, employee profiles that hold the compensation arrangement, and task workflows that fire before the first pay run rather than after it. The gross-up math is not the hard part. Remembering to do it in the window where it still works is. The running payroll guide covers where the gross-up entry fits in a pay cycle.

Common Gross-Up Mistakes

The first mistake on that list is a math error and the rest are process errors, which is a fair summary of how gross-ups actually go wrong at small companies. Nobody has trouble with the division. They have trouble remembering that the division needed to happen. The payroll automation guide covers which parts of this can be taken off a human's memory entirely.

Frequently Asked Questions