S-Corp Profit Sharing Contribution Deadline: March 15 and Extensions

An S-corporation’s profit-sharing contribution deadline is the due date of the corporation’s Form 1120-S, including extensions. For a calendar-year S-corp, that means March 15 of the following year, or September 15 if a timely Form 7004 extension was filed. As long as the money is deposited into the plan trust by that date, the contribution is deductible for the prior tax year.

March 15 Without an Extension, September 15 With One

Form 1120-S is due on the 15th day of the third month after the tax year ends, which lands on March 15 for calendar-year filers.1Internal Revenue Service. Starting or Ending a Business A profit-sharing contribution deposited into the plan trust by that date counts as a deduction for the prior year.

Most S-corp owners need more runway than that to close the books and settle on a contribution number. Filing Form 7004 before March 15 produces an automatic six-month extension and pushes the return deadline to September 15.2Internal Revenue Service. About Form 7004, Application for Automatic Extension of Time to File Certain Business Income Tax, Information, and Other Returns That extended date becomes the final funding deadline too. You don’t have to wait until September 15 to file the return; you just need the contribution in the trust by then.

Retroactive funding works because of the “deemed paid” rule in Internal Revenue Code Section 404(a)(6). A contribution is treated as if it had been made on the last day of the prior tax year, provided it is on account of that year and deposited before the return due date including extensions.3Office of the Law Revision Counsel. 26 U.S. Code 404 – Deduction for Contributions of an Employer to an Employees Trust or Annuity Plan and Compensation Under a Deferred-Payment Plan Close the books in December, work through the numbers over the following months, and wire the contribution any time before the extended due date. The deduction attaches to the prior year.

The deposit date is what controls, so build in a few business days. A wire that leaves your operating account on September 15 but settles in the plan trust on September 16 will not qualify.

The Plan Itself Has to Exist by the Same Date

A deposit into a plan that doesn’t exist buys you nothing. Under Section 401(b)(2), as amended by the SECURE Act, an employer can adopt a profit-sharing plan after the tax year closes and elect to treat it as if adopted on the last day of that prior year, so long as the plan is formally adopted before the tax return due date, including extensions.4Office of the Law Revision Counsel. 26 USC 401 – Qualified Pension, Profit-Sharing, and Stock Bonus Plans For a calendar-year S-corp with a filed extension, a plan can be established as late as September 15 and still support a deduction for the prior year.

The IRS has confirmed the mechanics in its guidance on post-year-end contributions: a calendar-year employer can decide in early 2026 to establish a plan retroactively for 2025, as long as the plan is adopted before the extended due date of the 2025 return.5Internal Revenue Service. Issue Snapshot – Deductibility of Employer Contributions to a 401(k) Plan Made After the End of the Tax Year

Adoption is paperwork, not a conversation with your advisor. You need an executed plan document (commonly a pre-approved prototype from a plan provider), a separate Employer Identification Number for the plan trust, and a corporate resolution authorizing the plan. All of this has to be done before the extended filing deadline for the retroactive election to hold.

How Much You Can Fund by the Deadline

Three separate caps govern the 2026 contribution. All three apply at once, so the binding number is the smallest.

For a single owner-employee the interaction is straightforward. If the owner pays herself $360,000 in W-2 wages, 25% is $90,000, but the $72,000 annual additions cap binds first and limits the contribution to $72,000. If W-2 compensation is $200,000, 25% yields $50,000, which is below $72,000, so the contribution tops out at $50,000. Take 25% of W-2 wages (capped at $360,000), then confirm the result does not exceed $72,000.

With rank-and-file employees in the plan, the 25% limit applies to total compensation paid to all participants, and the $72,000 cap applies independently to each participant’s account.

One substitution trap: profit-sharing allocations must be based on W-2 wages. The IRS requires S-corp owners who perform services for the company to take reasonable compensation as wages before non-wage distributions.7Internal Revenue Service. S Corporation Compensation and Medical Insurance Issues Distributions and other non-wage amounts cannot be used in the contribution calculation. Owners who hold W-2 wages down to save payroll tax are also shrinking the base they can contribute from.

What Happens If You Miss It

A contribution deposited after the extended due date cannot be deducted on the prior year’s Form 1120-S. It can only be deducted for the year it is actually deposited, which may defeat the tax plan the contribution was meant to serve.

When the S-corp has promised contributions to employees and then fails to deposit on time, the exposure is larger. Late deposits of employer contributions can be treated as prohibited transactions, carrying an initial excise tax of 15% of the amount involved for each year the transaction remains uncorrected, and an additional 100% tax if the problem is still not fixed.8Internal Revenue Service. 401(k) Plan Fix-It Guide – You Haven’t Timely Deposited Employee Elective Deferrals

Overfunding has its own penalty. Nondeductible contributions to a qualified plan draw a 10% excise tax under Section 4972, on top of the lost deduction, and the tax continues to apply each year the excess sits in the plan.

The IRS Employee Plans Compliance Resolution System offers a cure. The Self-Correction Program lets plans with established compliance procedures correct certain failures without IRS user fees, generally within three years for failures significant in the aggregate; insignificant failures can be corrected after that window.8Internal Revenue Service. 401(k) Plan Fix-It Guide – You Haven’t Timely Deposited Employee Elective Deferrals If self-correction is unavailable, the Voluntary Correction Program involves an IRS submission and a user fee.

Reporting Dates That Follow the Funding Deadline

Owner-only plans (one-participant plans) do not file the standard Form 5500. They file Form 5500-EZ, and only once total plan assets across all one-participant plans maintained by the employer exceed $250,000 at the end of the plan year.9Internal Revenue Service. Are Assets in Your Clients One-Participant Plans More Than $250,000 Below that threshold, no annual return is required unless it’s the plan’s final year. Once the threshold is crossed, Form 5500-EZ must be filed for each one-participant plan the employer maintains, even if a given plan is under $250,000.10Internal Revenue Service. Instructions for Form 5500-EZ

Plans covering employees beyond the owner file Form 5500 (or Form 5500-SF for small plans), due on the last day of the seventh month after the plan year ends — July 31 for a calendar-year plan. An extension is available by filing Form 5558.11Internal Revenue Service. About Form 5558, Application for Extension of Time to File Certain Employee Plan Returns

Keep the deposit confirmation. The single most useful piece of evidence that the funding deadline was met is the bank or custodial statement showing the date funds arrived in the plan trust, backed by a wire confirmation or cleared-check record. A corporate resolution authorizing the contribution amount or formula, along with the allocation worksheet and employee census, rounds out what an auditor expects. The amount reported on Form 5500 or 5500-EZ should tie to the deduction claimed on Form 1120-S.