Cash balance plan deadlines for 2026

The 2026 dates at a glance

The deadline calculator works out the same dates for other years. The rest of this page explains where each one comes from.

Adopting a plan after the year ends

Before 2020, a plan generally had to be signed by the last day of the year it was meant to cover. The SECURE Act changed that. IRC 401(b)(2) now lets a business that adopts a plan after the close of its tax year, but before the due date of its return including extensions, elect to treat the plan as adopted on the last day of that year.

So a sole proprietor who files an extension can adopt a 2026 plan as late as October 15, 2027, and an S corporation or partnership as late as September 15, 2027. Without an extension, those dates are April 15, 2027 and March 15, 2027.

What cannot be adopted after year end is a 401(k) salary deferral feature. A deferral election has to be made before the pay is earned. There is one narrow exception: an owner of an unincorporated business who is its only employee can make deferrals for a new 401(k)'s first year up to the return due date without extensions, April 15, 2027 for 2026. It does not cover S corporations or partnerships.

The December 31 payroll deadline for corporations

If your business is an S or C corporation, the plan counts only your W-2 wages. Distributions and profit left in the company do not count. Wages for 2026 have to be paid through payroll in 2026, so once the last payroll of the year has run you cannot add 2026 pay or reclassify a distribution as salary.

This is the one deadline that cannot be extended, and it arrives months before the others. An S corporation owner who wants a larger plan should look at salary before December 31, 2026, even though the plan itself can be signed much later. The trade-off between salary and payroll tax is covered in S corporation owners.

Sole proprietors and partners have no equivalent. Their plan pay is earned income, worked out from the year's profit after it ends.

The deduction deadline

Under IRC 404(a)(6), a contribution made after the year ends counts as made on the last day of the year if it is paid by the due date of the business's return, including extensions. That is the last day to contribute and still deduct the money for 2026.

Two practical points follow. The extended date only applies if an extension is actually filed. And the return that claims the deduction should not be filed until the contribution is final, because the amount deducted depends on what was actually paid in.

For S corporations and partnerships, whose returns are due in March, a business that does not extend has until March 15, 2027 to contribute. An owner adopting a plan late in the year often extends the return, which moves the date to September 15, 2027.

The minimum funding deadline

Separately from the tax deduction, the plan itself has a funding rule. IRC 430(j)(1) makes the year's minimum required contribution due 8½ months after the plan year ends: September 15, 2027 for a 2026 calendar-year plan.

For S corporations and partnerships that extend, this falls on the same day as the deduction deadline. For sole proprietors and C corporations it comes a month earlier, so the contribution has to be in the plan by September 15, 2027 even though the return may be due later.

In later years, a plan that had a funding shortfall in the prior year must also pay quarterly installments during the year. They do not apply in a plan's first year.

Form 5500-EZ

A one-participant plan files Form 5500-EZ once the combined assets of all the business's one-participant plans (a cash balance plan and a Solo 401(k) are added together) are more than $250,000 at the end of the plan year, and always for the plan's final year. It is due on the last day of the seventh month after the plan year ends, which puts the 2026 filing at August 2, 2027. Filing Form 5558 by then extends it to October 15, 2027.

A plan funded at six figures a year usually passes $250,000 in its second year, so most owners file from then on. The late filing penalty is $250 a day. For a plan adopted after year end under IRC 401(b)(2), the IRS instructions say no Form 5500-EZ is filed for that first year, though the actuary still completes the funding schedule for it. See Form 5500-EZ.

What happens each year after

The cycle repeats every year the plan exists:

• December 31: the plan year ends, and corporate payroll for the year closes.
• January: you send your pay for the year and the plan account's year-end statement.
• Spring: the enrolled actuary values the plan, signs the Schedule SB funding figures and sets the next range.
• By July 31 (or later with an extension): Form 5500-EZ, if required.
• By September 15: the minimum required contribution for the year just ended. For S corporations and partnerships that extend, this is also the deduction deadline.

The first time through, the dates stack up in the months after year end. Knowing them in advance is most of the work. See how to set up a cash balance plan for the steps that come before them.