The deadline that actually matters
Section 125 nondiscrimination test results are never filed with the IRS, so there is no filing deadline in the way you might expect from a tax form. That leads some employers to assume there is no real deadline at all. There is one, and it is more unforgiving than a filing date: your plan must be tested as of the last day of your plan year.
That date is what your results have to reflect. Testing after your plan year ends does not move the deadline back — it just means you are finding out where you stood on a date that has already passed, with no time left to change the outcome for that year.
The short version: your deadline is your plan year end date, not December 31 by default, not a tax season date, and not something your payroll provider's calendar necessarily tracks for you.
Your deadline depends on your plan year, not the calendar
Many cafeteria plans run on a calendar year, January 1 through December 31, which makes the deadline easy to remember. But plenty of plans don't. Plan years tied to a company's fiscal year, a renewal date set by a carrier, or a date chosen years ago for reasons no one currently at the company remembers, are all common. A plan year running July 1 to June 30 has a testing deadline of June 30, in the middle of the calendar year, not the end of it.
If you are not certain which dates apply to your plan, the plan document or Summary Plan Description (SPD) will state the plan year explicitly. Your broker or whoever originally set up the plan can also confirm it. This is worth checking before you assume a deadline, since guessing wrong in either direction either wastes time testing too early with incomplete data, or leaves you finding out too late.
Why the deadline only moves one direction
Testing early causes no harm. If you run a projection partway through the year and something looks off, you have room to fix it before the plan year closes. Testing late, or not at all, is a different story: once the plan year ends, the window to correct that year's results closes with it. There is no extension and no grace period.
What actually happens to a plan that fails a test is covered in full on our overview of what Section 125 testing is — the short version is that it affects only your highly compensated employees, but the financial and administrative cleanup for the employer can be significant. The deadline is the entire reason that page exists as a separate concern from the testing itself: the fix is usually straightforward once you know about a problem, but only if you know about it while the year is still open.
When mid-year testing should actually happen
"Mid-year" is a loose label. What actually matters is running a projection once enough of the plan year has happened for the numbers to mean something, while still leaving enough time afterward to act if the projection shows a problem.
For most employers, that lands around two-thirds of the way through the plan year. For a calendar-year plan, that's roughly late summer. Testing that early usually leaves a few months of runway, enough time to adjust elections, address a concentration issue, or otherwise correct course before the December 31 close. Testing much later than that starts to compress the window in which any correction is realistically possible.
There is no requirement to test mid-year. A single year-end test satisfies the annual compliance requirement on its own. Mid-year testing is a timing strategy, not a separate legal obligation, and its only purpose is preserving your ability to act.
FAQ
Is the testing deadline the same as a tax filing deadline?
No. Nondiscrimination test results are not filed with the IRS or any government agency, so there is no filing deadline in the usual sense. The deadline that matters is the last day of your plan year, because that is the date your plan's testing results reflect and the date after which corrective options for that year disappear.
What if our plan year doesn't end December 31?
Your testing deadline follows your plan year end date, whatever that is. A plan year running July 1 to June 30 has a testing deadline of June 30, not December 31. Check your plan document or ask your broker if you are not sure which dates apply to your plan.
How far before year-end should mid-year testing happen?
Enough of the plan year needs to have elapsed for the data to be meaningful, but enough time needs to remain afterward to act on the results. For most employers that means roughly two-thirds of the way through the plan year, which typically leaves a few months of runway to make corrections before the year closes.
Is there a grace period if we miss the deadline?
No. Once a plan year closes, that year cannot be corrected retroactively. There is no extension or grace period for nondiscrimination testing the way there sometimes is for other compliance filings. The only real safeguard is testing early enough in the plan year that a problem, if there is one, still has time to be fixed.