TL;DR: An outdated W-4 is not a payroll error, but employees rarely see it that way. When their withholding is wrong and a tax bill shows up in April, you are usually the first call they make. Employers can only withhold based on the W-4 currently on file and cannot force anyone to update it, but a few proactive habits limit the fallout. Exempt status expires every year and must be reset by February 15 if no new form arrives, and an IRS lock-in letter always overrides whatever the employee’s W-4 says.
There is a form sitting in your employees’ profiles right now that is very likely out of date, and when it ends up causing an issue at tax time, you are going to be the first call they make. Form W-4 is what employees use to tell you how much federal income tax to withhold from each paycheck. Life changes, but the form does not update itself. A marriage, a divorce, a new baby, a spouse changing jobs, or picking up a side gig can all shift how much should be withheld, and none of those events automatically trigger a new W-4. When the form no longer reflects reality, the employee either overwithholds, which is essentially an interest free loan to the government, or underwithholds, which generates a bill in April that they are usually not happy about.
Employers Can Only Withhold What the W-4 Says
As an employer, you are required to withhold based on whatever the current W-4 says, nothing more and nothing less. You are not required to prompt an employee to update it, and you cannot require them to update it either. But you are the one running payroll, so when the withholding turns out to be wrong, the employee’s frustration lands on your desk first, even though the form itself was theirs to maintain.
An Outdated W-4 Is Not a Payroll Error, But It Will Feel Like One
This is worth saying plainly: if an employee’s W-4 is out of date and they end up owing taxes, that is not a payroll error. You withheld exactly what the form on file instructed you to withhold. The problem is that the employee will not always see it that way. From their side, a surprise tax bill feels like something went wrong with their paycheck, and the easiest place to direct that frustration is the person who ran payroll all year. Knowing this in advance changes very little about your legal obligation, but it changes a lot about how you respond when the call comes in.
Life Events That Deserve a Proactive Nudge
Certain life events are common enough that they should trigger a proactive notification or reminder from you, even though you cannot require anyone to act on it. A welltimed nudge after a known life change, a new hire announcement, a benefits enrollment update, or an employee returning from leave, goes a long way toward reducing friction at the end of the year. It costs you almost nothing to send, and it gives the employee a fair chance to catch a mismatch before it compounds for months. guHRoo covers several of these same paycheck accuracy habits in 2026 HR and payroll pain points in South Carolina, where small process gaps like this one show up again and again.
The Exempt Status Reset Employers Must Track
If an employee claims exempt status, meaning zero federal income tax withheld at all, that election expires every single year. It only applies to the calendar year it was submitted. If the employee claimed exempt in January and does not give you a new Form W-4 claiming exempt again by February 15 of the following year, you are required to revert their withholding to the default rate, treated as single with no additional adjustments. That deadline moves to the next business day if February 15 falls on a weekend or holiday. This one is on you to track, not the employee. Missing it means you are withholding incorrectly on your own end, which is a very different problem than an employee simply forgetting to update their form.
When the IRS Steps In: Lock-In Letters
The IRS can issue a lock-in letter, which requires you to withhold at a specific rate for that employee regardless of what their W-4 currently says. If that happens, you are legally obligated to follow the IRS instruction, not the employee’s form, and you cannot reduce that withholding without IRS approval even if the employee submits a new W-4 asking for less. This is the one scenario where your normal rule, withhold based on whatever is on file, gets overridden entirely by federal instruction.
A Simple Audit to Protect Your Business
A few habits go a long way toward safeguarding yourself from these situations before they turn into a call you did not expect. Pull a list of employees whose W-4 is over two years old and flag them for a voluntary update reminder. You are not forcing anyone to change anything, but simply letting someone know it has been two years since they last completed the form often prompts a review they would not have thought to do otherwise. Add a W-4 review prompt into your open enrollment or January HR communications so it becomes a routine part of the calendar rather than a one-time effort. Make sure your onboarding process explains that the W-4 is the new hire’s responsibility to keep current, and document that conversation so there is a clear record it happened.
Building This Into Your Calendar
None of these steps require legal authority you do not already have, and none of them force an employee to do anything. What they do is create a paper trail of reasonable effort and give employees a real opportunity to catch a stale form before tax season turns it into a dispute. Treat the two year list, the January reminder, and the onboarding conversation as three recurring items on your HR calendar rather than something you only think about when a problem shows up.
A Quick Note on State Rules and Getting Help
Some states use their own state withholding certificate in addition to the federal W-4, and requirements vary by state. This article covers general federal withholding concepts and is meant as compliance information, not legal or tax advice. If you have received, or think you are about to receive, an IRS lock-in letter and are not sure how to handle it, that is a situation worth navigating with help rather than alone.
Frequently Asked Questions
What happens if an employee never updates their W-4?
Their withholding stays based on whatever information is already on file, even if it no longer matches their real tax situation. Over time this usually leads to either overwithholding, which just delays their own money being returned to them, or underwithholding, which can leave them with a balance due when they file. The employer is not at fault for withholding correctly according to an outdated form, but the employee often assumes otherwise.
Is the employer liable if a W-4 is outdated?
No. Employers are only required to withhold based on the current W-4 on file and are not responsible for prompting updates or for the tax consequences of a stale form. The exception is the employer’s own obligations, like resetting expired exempt status by February 15 or following an IRS lock-in letter, since those are the employer’s responsibility to track and act on regardless of what the employee does.
What happens if an employee doesn’t renew their exempt status by February 15?
If an employee claimed exempt status the prior year and does not submit a new Form W-4 claiming exempt again by February 15, the employer is required to revert their withholding to the default rate, treated as single with no additional adjustments. This deadline shifts to the next business day if it falls on a weekend or holiday, and it is the employer’s job to track it, not the employee’s.
Can employers require employees to update their W-4?
No. Employers cannot require an employee to submit a new W-4, even if the one on file is clearly outdated. What employers can do is send proactive reminders after known life events or on a routine schedule, which reduces the odds of a stale form causing a problem without crossing into requiring an update.
What is an IRS lock-in letter?
A lock-in letter is a notice the IRS sends when it determines an employee’s withholding does not match their income. It instructs the employer to withhold at a specific rate going forward, regardless of what the employee’s W-4 says, and the employer must follow it. The employer cannot reduce withholding below the IRS-specified rate without IRS approval, even with a new W-4 from the employee.
Make W-4 Reviews a Routine, Not a Reaction
Most of the friction around outdated W-4 forms is not a compliance failure, it is a missed reminder. A short list of employees whose forms are two years old, a prompt built into January communications, and a documented onboarding conversation cost very little and prevent most of the surprise calls that land on your desk every tax season. For a deeper look at how outdated forms affect employees directly, see guHRoo’s companion piece on an outdated W-4 could cost your employees, and check what dedicated payroll support could look like for your business with the Bound Payroll Employer Cost Calculator. If you have received or expect an IRS lock-in letter and are not sure how to handle it, reach out to guHRoo, since that is not a situation worth navigating alone.
