When Are Profit Sharing Contributions Due by Entity Type?

Profit-sharing contributions are due by the due date of your business’s federal income tax return for the year the contribution is for, including any filed extension, and the exact calendar date depends on your entity type. The rule comes from IRC Section 404(a)(6), which treats a contribution deposited by that deadline as if it had been made on the last day of the prior tax year.¹ It applies the same way to cash-basis and accrual-basis employers.²

So the answer depends on which return your business files. The sections below walk through each entity type on a calendar tax year. If your business runs on a fiscal year, the same logic applies to your fiscal return due date rather than the calendar dates shown.

Deadlines by Entity Type

S-Corporations (Form 1120-S)

The return is due the 15th day of the third month after the tax year ends. For calendar-year filers, that is March 15. A timely six-month extension moves the contribution deadline to September 15.³

Partnerships and Multi-Member LLCs (Form 1065)

Same timing as S-corporations: March 15 for calendar-year filers, extended to September 15.⁴

C-Corporations (Form 1120)

The return is due the 15th day of the fourth month after the tax year ends. For calendar-year filers, that is April 15. A six-month extension moves the deposit deadline to October 15. One exception: C-corporations with a fiscal year ending June 30 file by the 15th day of the third month instead.³

Sole Proprietors and Single-Member LLCs (Schedule C with Form 1040)

You file with your individual return, due April 15. A six-month extension pushes the contribution deadline to October 15.⁵

Two pairings fall out of this. S-corporations and partnerships share the March 15 / September 15 cycle. C-corporations and sole proprietors share April 15 / October 15. If your business recently changed its tax classification, your deadline changes with it. An LLC that elected S-corp treatment, for example, moves from the April 15 cycle to the March 15 one.

How a Filed Extension Moves the Deadline

Section 404(a)(6) uses the phrase “including extensions thereof” when defining the deposit window, so an extension of the return extends the contribution deadline by the same amount.¹ Corporations and partnerships use Form 7004 for an automatic six-month extension.⁶ Sole proprietors and single-member LLCs use Form 4868.⁵

The extension form has to be filed before the original return due date. If it is late or incomplete, the contribution deadline stays at the original date, not the extended one.

The extension gives you more time to file and fund the plan. It does not give you more time to pay the tax you owe. Interest and late-payment penalties can still run from the original due date if you underpay. Even so, filing the extension is standard practice for many owners who want the extra months to finalize contribution calculations, manage cash flow, and coordinate with the plan administrator. This is especially common with Solo 401(k) plans.

What Counts as a Timely Contribution

The money has to actually move. The contribution must be physically deposited into the plan’s trust or custodial account by the deadline. Booking the expense on your company ledger without transferring the cash does not satisfy the rule, and this is true whether you report on the cash or accrual method.²

The contribution also has to be allocated to the correct plan year, so the plan treats it as a prior-year deposit rather than a current-year one. In practice, that usually means a written resolution or similar authorization identifying the amount (or formula) and the plan year it applies to.

For accrual-basis employers, the all-events test adds a step. The liability must be fixed and determinable by the end of the tax year, which a formal board resolution or written determination adopted by December 31 can accomplish.⁷ The cash deposit can then follow by the filing deadline under the recurring item exception, so long as the pre-year-end resolution is in place.⁸ Cash-basis employers do not face the all-events test, because they deduct expenses when paid. A written allocation is still worth preparing, since it removes any ambiguity about which plan year the deposit belongs to.

Employee 401(k) Deferrals Are on a Different Clock

Everything above governs employer profit-sharing contributions. Employee elective deferrals, the amounts withheld from paychecks in a 401(k), do not follow the tax return deadline. The employer 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 figure is an outer limit, not a safe harbor. The Department of Labor expects most employers, especially those running electronic payroll, to deposit deferrals within a few business days. Holding employee money longer than necessary is treated as a prohibited transaction with its own penalty regime.

What Happens if You Miss the Deadline

A contribution deposited after the return deadline (including any extension) is not deductible for the prior year. It becomes a current-year contribution, which can crowd out the current year’s deductible limit.

If the contribution exceeds the deductible limit for the year it lands in, a 10% excise tax applies to the nondeductible portion sitting in the plan at the close of the employer’s tax year. The tax recurs annually until the excess is absorbed through future deductions.¹⁰ The excess itself is not lost; it can be carried forward and deducted in later years subject to the same cap.¹

Late deposits of employee deferrals carry stiffer consequences because of the prohibited transaction treatment: an initial 15% excise tax on the amount involved for each year the violation remains uncorrected, with an additional 100% tax possible if the problem is not fixed.¹¹ Correction programs exist on both sides. The IRS Self-Correction Program covers operational errors in qualified plans without an application or fee, generally requiring significant errors to be corrected before the end of the third plan year after the failure.¹² The Department of Labor’s Voluntary Fiduciary Correction Program handles late deferral deposits, offering relief from civil enforcement and conditional relief from the prohibited transaction excise tax once the employer deposits the funds with lost earnings and files the required documentation.¹³

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. Issue Snapshot – Deductibility of Employer Contributions to a 401(k) Plan Made After the End of the Tax Year
3
Internal Revenue Service. Starting or Ending a Business 3
4
Internal Revenue Service. 2025 Instructions for Form 1065
5
Internal Revenue Service. Form 4868 – Application for Automatic Extension of Time to File U.S. Individual Income Tax Return
6
Internal Revenue Service. Instructions for Form 7004 (Rev. December 2025)
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
Office of the Law Revision Counsel. 26 U.S. Code 4975 – Tax on Prohibited Transactions
12
Internal Revenue Service. Correcting Plan Errors – Self-Correction Program (SCP) General Description
13
U.S. Department of Labor. Fact Sheet – Voluntary Fiduciary Correction Program