Short answer
W-2 workers usually owe because withholding was set too low: two jobs or a working spouse left out of Form W-4, bonuses withheld at the 22% flat rate, or side income with nothing withheld. File on time, pay what you can, use a short-term plan or Simple Payment Plan for the rest, then update your W-4.
Key takeaways
- Each employer withholds as if its job were your only income, so two jobs or two working spouses without Step 2 of Form W-4 often leads to a balance.
- Employers may withhold a flat 22% on bonuses and commissions, which falls short if your tax rate is higher.
- You generally avoid the underpayment penalty if withholding covered 90 percent of this year’s tax or 100 percent of last year’s (110 percent for higher incomes).
- A short-term plan (up to 180 days (IRS.gov, 2026)) or a Simple Payment Plan covers most W-2 balances without a financial statement.
- If the IRS sends your employer Letter 2800C, your withholding is locked at the IRS rate until the IRS approves a change.
Why W-2 workers end up owing
Your employer withholds based on the Form W-4 you gave it, and only on the pay it sends you. When the bill comes at filing time, one of these is usually the reason:
- Two jobs, or a working spouse. Each employer withholds as if its paycheck were your only income, so each one applies the standard deduction and lower brackets again. The 2026 Form W-4 says Step 2 is for anyone who holds more than one job at a time or is married filing jointly with a spouse who also works, because “the correct amount of withholding depends on income earned from all of these jobs.” Skipping Step 2 is the most common cause of a surprise balance.
- Bonuses and commissions. Publication 15 (2026) lets employers withhold a flat 22% on supplemental wages such as bonuses, commissions and overtime pay (37% on supplemental wages above $1 million in a year). If your top tax rate is higher than 22%, that bonus leaves a gap.
- Side income with no withholding. Freelance, gig, rental, interest or investment income adds tax that no paycheck covered. For gig and 1099 work, see owing after a 1099 year.
- A W-4 that no longer fits. Credits or deductions entered in Steps 3 and 4(b) that you no longer qualify for, or a marriage, divorce or new job since you last filled it out.
- Retirement withdrawals or unemployment pay with too little or no tax withheld.
None of this means you did anything wrong. It does mean the balance will come back next year unless the W-4 changes. If you are not sure what you owe, start with how much you owe the IRS.
The underpayment penalty and the safe harbors
Owing at filing time is not a penalty by itself. The underpayment of estimated tax penalty applies when withholding and estimated payments during the year fell short. According to the Instructions for Form 2210 (2025), you generally owe no penalty if:
- the tax on your return minus withholding is less than $1,000 (IRS.gov, 2026); or
- your withholding and timely estimated payments covered the smaller of 90 percent of this year’s tax or 100 percent of last year’s tax (110 percent if last year’s adjusted gross income was over $150,000, or $75,000 if married filing separately); or
- you had no tax liability for the prior year, were a U.S. citizen or resident all year, and that return covered 12 months.
A useful detail for W-2 workers: withholding is generally treated as paid in four equal parts on the estimated tax due dates, unless you choose to show the actual dates. So raising your withholding late in the year still counts as if it had been spread evenly across the year, while a late estimated payment does not.
The penalty works like interest on each quarterly shortfall, using the quarterly underpayment rate (the federal short-term rate plus 3 percentage points, 7% (IRS.gov, Jul-Dec 2026) this quarter). The IRS figures it and sends a notice. It “generally cannot be waived due to reasonable cause,” but it can be reduced for a casualty, disaster or other unusual circumstance, or if you retired after age 62 or became disabled and had reasonable cause.
Paying this year's bill
File on time even if you can’t pay in full. The failure-to-file penalty is 5% (IRS.gov, 2026) a month, ten times the 0.5% (IRS.gov, 2026) monthly failure-to-pay penalty. Then pick a way to pay the rest:
| Option | Fits when | Key terms |
|---|---|---|
| Pay in full | You can cover it from savings | IRS Direct Pay from a bank account is free and stops further penalties and interest. |
| Short-term payment plan | You can pay in full within 180 days (IRS.gov, 2026) | $0 (IRS.gov, 2026) setup fee; apply online if you owe less than $100,000 (IRS.gov, 2026). |
| Simple Payment Plan (formerly the streamlined installment agreement) | You owe $50,000 (IRS.gov, July 2026) or less in tax, penalties and interest | Monthly payments, no financial statement; setup fee $29 (IRS.gov, 2026) for direct debit applied online. |
| Larger balance or several years | Over the Simple Payment Plan limit | Usually needs a financial statement; see relief by balance size. |
While a plan is in effect, the failure-to-pay penalty drops to 0.25% (IRS.gov, 2026) a month if you filed on time; interest continues. Apply yourself through the IRS Online Payment Agreement. Plans are compared in IRS payment plans compared, and if the April deadline is close, read can’t pay by April 15.
The notices follow a set order: CP14 is the first bill, CP501 and CP503 are reminders. Setting up a plan at the CP14 stage is the easiest point to stop the sequence.
Fixing your withholding so it doesn't happen again
A payment plan for last year does not fix this year. If your withholding is still short, a second balance arrives next April, and a new balance while you are on a plan can put that plan at risk (see owing two years in a row).
- Gather recent pay stubs. The IRS Tax Withholding Estimator asks for your most recent pay stubs for each job, your spouse’s if you file jointly, and your last return if you have other income or itemize.
- Run the Tax Withholding Estimator. It takes about 25 minutes, does not ask for your name or Social Security number, and produces a pre-filled Form W-4.
- Fill out Step 2 if two jobs are involved. Use the estimator, the Multiple Jobs Worksheet, or, with only two jobs in total, check the Step 2(c) box on both W-4s. Complete Steps 3 and 4(b) on only one W-4, ideally the highest-paying job.
- Use Step 4(a) or 4(c) for the rest. Enter other income in Step 4(a), or a flat extra amount per paycheck in Step 4(c).
- Give the new W-4 to your employer and check your next pay stub. The IRS suggests checking every January and after a new job, marriage, divorce or a child. If you change it mid-year, recheck in late December.
Want the longer prevention checklist? See the best ways to avoid owing next year.
Letter 2800C: when the IRS sets your withholding
If the IRS decides an employee is not having enough tax withheld, it can send the employer a lock-in letter, Letter 2800C, with a copy for the employee. The IRS letter page says the employer should start withholding at the rate in the letter “effective 60 days from the date of this letter,” and Publication 15 says the employer must hand over the employee copy within 10 business days.
- Once the lock-in takes effect, the employer cannot lower your withholding without IRS approval and must disregard a new W-4 that would reduce it.
- You can still increase withholding with a new W-4.
- To change the lock-in, send a new Form W-4 with a supporting statement to the IRS address on the letter, or call the number in the letter (the IRS page lists 855-839-2235, weekdays 8 a.m. to 5 p.m.).
A lock-in letter is a withholding instruction, not a bill and not a sign of an audit. But it usually means past years were under-withheld, so check for balances on your IRS account transcript.
Example: two incomes, one bill
Penalty check: 90 percent of this year’s tax is $12,780; 100 percent of last year’s is $12,000. The smaller figure, $12,000, is the target. Withholding of $10,900 fell $1,100 short, and the balance is over $1,000, so a modest underpayment penalty is likely.
Paying it: they set up a short-term plan online and pay $1,100 a month for three months ($3,300), plus interest and the reduced failure-to-pay penalty.
Fixing it: to cover a similar gap next year, they need about $3,300 more withheld. With 24 paychecks left at Sam’s job, that is $3,300 / 24 = $137.50, entered in Step 4(c) of his W-4, or they check the Step 2(c) box on both W-4s and rerun the estimator.
When this is a do-it-yourself fix, and when it isn't
A one-year W-2 balance under the Simple Payment Plan limit is usually a do-it-yourself fix: file, set up a plan online, update the W-4. A professional is worth considering when the balance covers several years, when a CP2000 says the IRS has income you didn’t report (see disputing an IRS balance), when a lock-in letter is wrong and the IRS has not answered, or when you have received a final notice of intent to levy. Our guide do I need a tax professional? walks through the decision. Not sure? Get a free review; if the IRS online tools will solve it, we will tell you.
Frequently asked questions
Usually because withholding was set too low: two jobs or a working spouse not entered in Step 2 of Form W-4, bonuses withheld at the 22% flat rate when your rate is higher, or other income with no withholding. Run the IRS Tax Withholding Estimator and submit a new W-4.
There can be an underpayment penalty, figured on Form 2210. You generally avoid it if you owe less than $1,000 after withholding, or if withholding covered 90 percent of this year’s tax or 100 percent of last year’s (110 percent above $150,000 of adjusted gross income).
No. A bonus is taxed as ordinary income at your normal rates. Employers may withhold a flat 22% on it, or 37% on supplemental wages above $1 million. If your actual rate is higher than 22%, you will owe the difference when you file.
Yes. If you can pay within 180 days (IRS.gov, 2026), a short-term plan has no setup fee. If you owe $50,000 (IRS.gov, July 2026) or less, a Simple Payment Plan lets you pay monthly without a financial statement. Both can be set up online.
Letter 2800C tells your employer to withhold at a rate set by the IRS, effective 60 days from the letter’s date, because the IRS believes your W-4 leads to too little withholding. Your employer cannot lower it without IRS approval; you can contact the IRS to request a change.
Change it, but in the other direction: you need more withholding, not less. Use Step 2 for multiple jobs and Step 4(c) for a flat extra amount per paycheck. The Tax Withholding Estimator produces a filled-in W-4.
Sources
- IRS Form W-4 (2026), Employee's Withholding Certificate
- IRS Publication 15 (2026), Employer's Tax Guide (supplemental wages; lock-in letters)
- IRS: Tax Withholding Estimator
- IRS Instructions for Form 2210 (2025)
- IRS: Underpayment of estimated tax by individuals penalty
- IRS: Understanding your Letter 2800C
- IRS: Payment plans; installment agreements
- IRS: Simple payment plans for individuals and businesses
- IRS: Online Payment Agreement application
We check every figure against IRS.gov and log changes on the key figures page.
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This page is general information about IRS rules, not tax or legal advice for your situation. IRS figures change; each one links to its official source and the date we last checked it.