When Are Profit Sharing Contributions Due by Entity Type?

A profit-sharing contribution is deductible for a given tax year as long as the employer deposits the money into the plan’s trust by the business’s federal income tax return due date for that year, including any filed extensions. The profit sharing contribution deadline by entity type therefore tracks the return due date for each business form: March 15 or April 15 without an extension, and September 15 or October 15 with one. The rule comes from IRC Section 404(a)(6), which treats a timely deposit as if it had been made on the last day of the prior tax year.¹

Deadlines by Entity Type

Every date below assumes a calendar tax year ending December 31. Fiscal-year businesses follow the same logic, tied to whatever return due date applies to their fiscal year.

S-corporations (Form 1120-S). Return due March 15. With a six-month extension, the contribution deadline moves to September 15.²
Partnerships and multi-member LLCs taxed as partnerships (Form 1065). Return due March 15. Extended deadline September 15.³
C-corporations (Form 1120). Return due April 15. Extended deadline October 15. C-corporations with a fiscal year ending June 30 file by the 15th day of the third month instead.²
Sole proprietors and single-member LLCs (Schedule C, Form 1040). Return due April 15. With a six-month extension, the contribution deadline moves to October 15.⁴

S-corporations and partnerships share the earlier March 15 / September 15 track. C-corporations and sole proprietors share the later April 15 / October 15 track. If your business recently changed classification, for example an LLC that elected S-corp treatment, the contribution deadline shifts with the new return due date.

How an Extension Moves the Deadline

Section 404(a)(6) includes the phrase “including extensions thereof,” so a validly filed extension pushes the contribution deadline out by the same amount as the filing deadline.¹

Corporations and partnerships file Form 7004 for an automatic six-month extension.⁵ Sole proprietors and single-member LLCs file Form 4868 for a six-month individual extension.⁴ In both cases, the extension request must be submitted before the original return due date. A late or improperly completed extension leaves the contribution deadline at the original date.p>

One limit worth naming. The extension gives you more time to file the return and fund the plan. It does not extend the time to pay income taxes already owed. If you underpay, interest and late-payment penalties can still accrue from the original due date.

Filing the extension is a common planning step even when the return could be finished earlier. The extra months give the business time to finalize contribution calculations, manage cash flow, and coordinate with the plan administrator. This shows up often with Solo 401(k) plans, where the owner is both employer and participant.

What Counts as a Timely Deposit

The money must physically arrive in the plan’s trust or custodial account by the deadline. Booking the expense on the company ledger without moving the cash does not satisfy Section 404(a)(6), and this holds for both cash-basis and accrual-basis employers.⁶

The employer also has to allocate the contribution to the correct plan year so the plan treats the funds as a prior-year deposit. In practice that means a written resolution or similar authorization identifying the contribution amount or formula and the plan year it applies to.

Accrual-basis employers face a tighter documentation standard. The all-events test requires the liability to be fixed and determinable before the end of the tax year, which a board resolution or written determination adopted by December 31 accomplishes.⁷ The cash deposit itself can follow later under the recurring item exception, which lets economic performance occur by the filing deadline, but the resolution has to be in place before year-end.⁸

Cash-basis employers are not subject to the all-events test, because they deduct expenses when paid. Under 404(a)(6), the contribution just needs to be paid by the filing deadline and allocated to the prior plan year.⁶ Even so, a written allocation resolution is cheap insurance if the IRS ever asks which year the deposit belongs to.

Adopting a New Plan After Year-End

Before 2020, employers had to adopt a written retirement plan document by December 31 of the first plan year. The SECURE Act eliminated that requirement. A business can now adopt a brand-new profit-sharing or 401(k) plan after the tax year ends, up to the tax return filing deadline including extensions, and still deduct the contribution for the prior year.⁶

An S-corp owner who files an extension, for example, could adopt a plan and fund it as late as September 15 and take the deduction against the prior year’s income. The plan document, the contribution, and the allocation all have to be in place by that extended deadline.

Employee Deferrals Are on a Different Clock

The return-based deadline covers employer profit-sharing contributions only. Employee elective deferrals, meaning the money withheld from paychecks in a 401(k), follow a much tighter rule. Employers must deposit those funds as soon as they can reasonably be segregated from company assets, and no later than the 15th business day of the month after the paycheck.⁹ The 15th-business-day date is an outer limit rather than a safe harbor. Confusing the deferral deadline with the profit-sharing deadline is a common and expensive mistake.

Missing the Deadline

A contribution that misses the return due date, including extensions, is not deductible for the prior year. It can still be carried forward and deducted in a future year within the applicable limits, but a 10% excise tax applies to any nondeductible contribution sitting in the plan at the close of the employer’s tax year, and it recurs annually until the excess is absorbed.¹⁰

If you have already missed a deadline, correction programs exist through both the IRS and the Department of Labor. The IRS Self-Correction Program lets employers fix operational errors in qualified plans without an application or fee, and for significant errors the correction generally must be completed before the end of the third plan year after the failure.¹¹ Late deposits of employee deferrals are handled through the Department of Labor’s Voluntary Fiduciary Correction Program, which requires the employer to calculate and pay lost earnings on the late funds.¹²

1
Office of the Law Revision Counsel. 26 USC 404 – Deduction for Contributions of an Employer to an Employees Trust or Annuity Plan and Compensation Under a Deferred-Payment Plan
2
Internal Revenue Service. Starting or Ending a Business 3
3
Internal Revenue Service. 2025 Instructions for Form 1065
4
Internal Revenue Service. Form 4868 – Application for Automatic Extension of Time to File U.S. Individual Income Tax Return
5
Internal Revenue Service. Instructions for Form 7004 (Rev. December 2025)
6
Internal Revenue Service. Issue Snapshot – Deductibility of Employer Contributions to a 401(k) Plan Made After the End of the Tax Year
7
Internal Revenue Service. Publication 538 (01/2022), Accounting Periods and Methods
8
Internal Revenue Service. Rev. Rul. 2007-12
9
U.S. Department of Labor. ERISA Fiduciary Advisor
10
Office of the Law Revision Counsel. 26 U.S. Code 4972 – Tax on Nondeductible Contributions to Qualified Employer Plans
11
Internal Revenue Service. Correcting Plan Errors – Self-Correction Program (SCP) General Description
12
U.S. Department of Labor. Fact Sheet – Voluntary Fiduciary Correction Program