Need to Know Tax › Deductions, credits, and gains
Withholding
Why your refund wasn’t what you expected: withholding
For anyone with more than one W-2 in the house: two jobs, two earners, or part-time work. Nobody did anything wrong, and the bill still arrived. Six payroll departments never talked to each other, and the IRS adds it all up in April.
Every tax season brings a few bad surprises, and this is one of the most common. Nobody did anything wrong, and the bill still arrived. Picture six W-2s at $15,000 apiece, each with a zero in Box 2, the federal tax withheld. Six payroll departments never talked to each other, and the IRS adds it all up in April. The same thing happens, more quietly, to married couples who both work. Some preparers call it the Box 2 Bermuda Triangle: the withholding that should have been there simply vanished.
Why it happens
Each employer figures withholding as if theirs is your only job. Payroll multiplies this paycheck out over a year, subtracts the standard deduction, and withholds tax on whatever is left. A $15,000-a-year job does not even reach the $16,100 standard deduction for a single filer, so the system sees nothing worth withholding. Social Security and Medicare still come out; federal income tax does not. Then the six jobs become one $90,000 income with one standard deduction. The right withholding for each job was that job’s share of the tax on everything.
Worked example: six jobs, one standard deduction, 2026
| Single filer | Each job | All six |
|---|---|---|
| Wages (Box 1) | $15,000 | $90,000 |
| Federal tax withheld (Box 2) | $0 | $0 |
| Taxable income after the $16,100 standard deduction | $0 | $73,900 |
| Federal tax actually owed | — | about $11,000 (10%, 12% and 22% brackets) |
| What each job should have withheld | about $1,800 a year, $70 a biweekly paycheck | about $11,000 |
| Colorado, at 4.40% on the same $73,900 | — | about $3,250, also largely unwithheld |
| Balance due in April, plus underpayment penalty | about $14,250 federal and state |
Rounded. Each payroll system did exactly what the W-4 said. The overall federal rate is only about 12%; it is the fact that none of it was paid in that makes April hurt.
Two-earner couples get a gentler version. Each employer withholds as if that paycheck is the household’s only income, with the full joint standard deduction and the lowest brackets. Together, the second income lands in the 22% or 24% bracket while both employers withheld as if it were taxed at 12%.
Worked example: two earners, $70,000 and $60,000
| What each employer assumed | What is true | |
|---|---|---|
| Standard deduction applied to this paycheck | $32,200 at each job | $32,200 once |
| Brackets used | 10% and 12%, starting over at each job | 10% and 12%, once: a second $24,800 at 10% that does not exist |
| Total withheld by both employers | about $6,900 | |
| Tax on $130,000 jointly | about $11,250 | |
| Shortfall in April | about $4,350 |
Rounded. The Step 2 checkbox on both W-4s fixes most of this; it tells each payroll to use half the standard deduction and half the brackets. For incomes this close, it lands within a few hundred dollars.
The W-4 fixes
Step 4(c), extra withholding. The most reliable fix for multiple jobs. Figure the tax on your total income from all jobs, divide it among them, and enter the per-paycheck amount in Step 4(c) of a new W-4 for each employer. In the six-job example, that is about $70 a biweekly paycheck at each job, added on top of whatever the tables say. Or put the whole extra amount at the job with the biggest paycheck; the IRS does not care which employer sends the money.
Step 2, the two-jobs checkbox. For couples who both work, or one person with two similar jobs, checking the box in Step 2 on both W-4s tells each employer to withhold as if the standard deduction and the brackets were cut in half. It works well when the two incomes are close. When one spouse earns much more, Step 4(c) on the larger job is the better tool, and the box should be checked on neither.
Check the math once a year. The IRS Tax Withholding Estimator at IRS.gov does the arithmetic from your latest pay stubs. In October there are still paychecks left to make up a shortfall. A new W-4 takes effect within a pay period or two, and it can be changed as often as you like.
If it has already happened
File on time whether or not you can pay; the penalty for filing late is far larger than the penalty for paying late. Pay what you can. For the rest, an installment agreement request can go in with the return itself, so the balance is paid monthly; for balances under $50,000 the IRS approves it online without a conversation. Interest and penalties run until it is paid, but the collection letters stop. Then fix the W-4s the same week, before the second year’s balance lands on top of the first year’s payment plan.
Behind the scenes
The first thing a preparer looks at on a stack of W-2s is not Box 1. It is Box 2 divided by Box 1, job by job. A ratio near zero on a job that pays real money says the W-4 was never set up for a second income, and the balance due can be predicted before the return is finished. The client sees a tax bill. The preparer sees six W-4s that need the same fix. The employer made no mistake; payroll did what the W-4 said. The second check is Box 17, the state withholding, because the Colorado version of the same problem arrives in the same envelope.
The Colorado side
Colorado withholding is figured job by job too, around the flat 4.40%, using the state’s own certificate, Form DR 0004, or the federal W-4 if none is filed. Because the rate is flat there is no bracket problem, but the standard deduction problem is the same: each employer assumes its paycheck gets the whole deduction, so several small jobs withhold nothing for Colorado either. In the six-job example, about $3,250 of state tax arrives unwithheld. Extra Colorado withholding per paycheck goes on the DR 0004, and from 2026 employers continue withholding Colorado tax on overtime even though the federal deduction applies.
What to bring your preparer
- Every W-2, including from jobs that lasted a few weeks
- For a fall checkup: the most recent pay stub from each current job, showing year-to-date wages and withholding
- The W-4 on file at each job, if you have a copy, or what you remember choosing
- Your spouse’s pay stubs, since the fix is figured on the household
- Any other income with no withholding: a side business, interest, a pension
- If a balance is already due: how much you can pay now, for the installment request
Questions people ask
My employer didn’t take out any federal tax. Did they make a mistake?
Probably not. If the job alone pays less than the standard deduction, the tables withhold nothing. The W-4 has to tell payroll about the other income, through Step 2 or Step 4(c).
I claimed “0” on my W-4. Why wasn’t that enough?
The W-4 has not had allowances since 2020. With the new form, the only ways to raise withholding are the Step 2 checkbox, extra dollars in Step 4(c), or listing other income in Step 4(a).
We both work. Should we both check the Step 2 box?
Yes, both, if your incomes are reasonably close. If one of you earns much more, leave the box unchecked and put extra withholding in Step 4(c) at the higher-paying job instead.
Is there a penalty for owing in April?
Only if the amount paid in during the year was below both safe harbors: 90% of this year’s tax, or 100% of last year’s (110% above $150,000 of AGI). The penalty is interest-like, a few percent of the shortfall; the balance itself is still due April 15.
Can I just make an estimated payment instead of changing the W-4?
Yes, but withholding is better: it counts as paid evenly through the year whenever it comes out, while an estimated payment counts only on the day it is made. A W-4 change in October catches up; a January estimate does not.
Box 2 divided by Box 1, job by job
That one ratio, run on each W-2, predicts the April surprise before the return is finished. If a job that pays real money shows nearly nothing withheld, the W-4 was never set up for a second income, and a new one takes ten minutes.