September 15 and the tax return are two clocks

Today is March 15, 2026. For a calendar-year S corporation or partnership, this is the original due date of the 2025 return, subject to the rule that moves a due date off a weekend or holiday to the next business day. Many of those returns will be extended today rather than filed. The extension is a tax-return act. It does not fund a cash balance plan, and it does not measure the minimum required contribution. Later this year, September 15, 2026 will sit on the calendar as the typical minimum-funding date for a 2025 calendar-year defined benefit plan and, for an extended S corporation or partnership, as the extended filing date as well. Two clocks can strike on the same morning and still be two clocks. This briefing is about keeping the jobs apart while the first of those mornings is happening.

Sterling Pension Group is a third-party administrator. We are not an actuarial firm. An independent Enrolled Actuary certifies the minimum required contribution and the deductible maximum, and signs Schedule SB. Your CPA signs the return, or prepares it for you to sign. We do not do either signature. This briefing is not tax, legal, or actuarial advice. It is a description of two statutory jobs that owners merge because both involve "the pension payment."

The funding clock

A defined benefit plan, including a cash balance plan, is subject to minimum funding. For a calendar-year plan, the minimum required contribution for a plan year is generally due 8.5 months after the year ends. For the 2025 year, that date is September 15, 2026. The payment is made to the plan's trust, in at least the amount the Enrolled Actuary determines. It is not made to the owner's IRA, and it is not satisfied by a journal entry that debits pension expense and credits accrued liabilities. If the trust account is not open, the funding clock is already a practical problem, not a theoretical one.

Miss the minimum and the plan has an unpaid minimum required contribution. The initial excise tax is 10 percent of the unpaid amount. If the deficiency is not corrected during the taxable period, a further tax can apply that is large enough to dominate the original planning idea. Liens and reporting consequences exist in more severe cases. None of that is cured by having filed a valid extension of the income-tax return. None of it is cured by intending to deduct a larger amount later. The funding payment is a legal obligation of the plan's sponsor to the plan. The plan lifecycle after adoption is, in part, the annual repetition of this obligation. It is not a surprise reserved for plans that are in trouble. Healthy plans fund the minimum every year.

Quarterly installments can pull cash forward. When a plan has a funding shortfall, the statute can require a portion of the minimum to be paid 15 days after the end of each quarter. The dates in a calendar year fall in April, July, October, and January. Not every small cash balance plan owes them. A plan that is well funded relative to its funding target may not. The actuary's work, not a blog post and not this briefing, says whether your plan is in that group. If a quarterly was due and missed during 2025, March is not the time to discover it by accident. Ask for the funding schedule in writing. If nothing was due until September 15, get that conclusion in writing too, so a cautious bookkeeper does not wire the wrong amount on the wrong day and a casual owner does not wire nothing.

The amount of the minimum is not the $280,000 defined benefit dollar limit that applied in 2025, and it is not the $290,000 limit that applies in 2026. Those are limits on the annual benefit, explained by the IRS on the defined benefit limits page. The minimum is the result of the funding method, the plan's assets, the benefit the document actually promised, and the assumptions the actuary is required to use. Two plans with the same owner age can have different minimums because one took a large credit and the other took a small one, or because one trust earned the interest credit and the other did not. Investment losses can raise the minimum. They do not create an excuse to skip it.

The deduction clock

The deduction clock answers a different question: by when must the employer pay a contribution in order to deduct it on the 2025 return. The general rule treats a payment made by the due date of the return, including extensions, as made on the last day of the tax year, if it is on account of that year. For an S corporation or partnership that files today, without extending, today is that deadline, again subject to any weekend or holiday convention the CPA applies. A deduction claimed on a return filed this week, for a contribution that is still a plan to wire next Thursday, is a deduction in search of a payment. Do not file the number and fund it later because the funding statute would have allowed September. The deduction statute used the deadline you actually used.

For an employer that extends, the deduction clock moves. An S corporation or partnership extension commonly runs to September 15, 2026. A sole proprietor's extension commonly runs to October 15, 2026. The contribution still has to be paid to the trust by the extended date you are relying on. The extension form itself does not move money. Filing Form 7004 and then forgetting the wire until the week the extended return is due is how funding and deduction get tangled: you may still be inside the deduction date and outside a quarterly funding date, or you may hit both dates on September 15 and discover the custodian needs two days you do not have. Start the wire instructions in the summer if the amount is final. Custodian reviews are slower when every other extended taxpayer is funding at once.

The deductible maximum is its own certified number. It can be higher than the minimum. Employers often contribute the minimum only, or some amount between minimum and maximum that matches cash and the formula. Contributing the maximum is not required just because it is deductible. Contributing above the maximum creates a deduction problem even if the plan is delighted to hold the cash. The CPA should not deduct an illustrative figure. If a January sketch showed a neighborhood of $190,000 or $320,000 or any other round teaching number, that sketch was illustrative. The return uses the actuary's maximum for 2025, under 2025 limits, and only to the extent the cash actually arrived in time.

2025 limits are the ones that govern that certification. Deferrals $23,500. Ordinary catch-up $7,500. Ages 60 through 63, $11,250. Defined contribution annual additions $70,000. Compensation cap $350,000. Defined benefit dollar limit $280,000. IRA limit $7,000. The release for those figures is IR-2024-285. The 2026 limits are already in force for the year now underway: deferrals $24,500, ordinary catch-up $8,000, ages 60 through 63 still $11,250, annual additions $72,000, compensation cap $360,000, defined benefit dollar limit $290,000, IRA limit $7,500, IRA catch-up $1,100. They come from IR-2025-111 and Notice 2025-67. They do not increase the 2025 deductible maximum. The COLA page shows both years. Circle the year of the return before you read down the column.

Publication 560 walks small employers through the idea that retirement contributions are deducted by the employer under rules that are stricter than a general accrual. Use it to keep the conversation with the CPA on the same vocabulary. It will not compute your maximum. The enrolled actuary will. If both a pension and a 401(k) covered the same people, ask the actuary specifically whether the combined-plan deduction limit changed the maximum. Adding $70,000 to a pension illustration is not that analysis. Elective deferrals and employer profit sharing are not treated identically in it. PBGC coverage can change it, and coverage is plan-specific. The PBGC coverage page is the starting map. A covered plan and an exempt plan can both have a minimum-funding clock. They may not have the same deduction arithmetic.

Same day, two jobs, and a third clock you should not fold in

Picture September 15, 2026, for an S corporation that extended. In the morning the minimum funding contribution may be due. The same day, the extended return may be due, and the deduction may depend on a contribution paid by that date. You can satisfy both jobs with one wire if the amount is at least the minimum, not above the deductible maximum, paid to the right trust, and reflected on the return the CPA is about to file. You can also satisfy one and fail the other. A wire that meets the minimum but is larger than the amount the CPA was told, or smaller than the amount the CPA deducted, is a reconciliation problem. A return that deducts the right amount while the wire went to a personal brokerage account is a failed payment. A wire that funds the minimum in full, while the return is extended again in someone's imagination and never filed, does not file the return.

You can also do the jobs at different times, which is often cleaner. Fund the minimum in June, when the actuary's number is final and the custodian is not in the September queue. Deduct it on the extended return in September, assuming the payment date satisfies the deduction rule, which a June payment will. Or fund exactly the deductible amount you intend to claim, if it is at least the minimum, a few weeks before the return is filed, and send the CPA the custodian confirmation before the return is released. What you should not do is treat "September" as a single task on a phone reminder. Write "fund at least the minimum" and "confirm the deduction matches the wire" as two lines. The deadline calendar should already look like that. If it does not, fix the calendar today while you are looking at an original due date and can feel why mushy reminders fail.

Form 5500 is the third clock, and it is neither of the two. For a 2025 calendar-year plan it is generally due July 31, 2026, extended to October 15, 2026 with Form 5558. The IRS Form 5500 corner and the Department of Labor's filing guidance describe that return. Filing it does not fund the plan. Funding the plan does not file it. An extension of the tax return does not extend it. Schedule SB, which the Enrolled Actuary signs, rides with the Form 5500 and reports the actuarial numbers. It is still not the deduction. The CPA may rely on it. The CPA does not file it by attaching it to Form 1120-S in place of the Department of Labor filing. Administration includes making sure the actuary, the CPA, and the filer of the 5500 are not each assuming another party pushed the button.

Roth catch-up belongs on none of these clocks. It became operational on January 1, 2026, for 401(k) catch-up contributions of participants whose 2025 FICA wages from the sponsoring employer were over $150,000. It changes the tax character of the $8,000 ordinary catch-up or the $11,250 age 60 through 63 catch-up in the current year. It does not change the 2025 minimum funding contribution. It does not change the cash balance pay credit. If today's filing season email from a payroll company is about Roth, answer it with the payroll company. Do not let it delay a funding wire or an extension.

Who the taxpayer is remains part of the deduction clock only. The employer deducts the employer contribution. An S corporation owner does not also deduct it on Schedule C. A partner does not deduct the partnership's contribution a second time on the 1040. A sole proprietor does report it on the owner's return, because the proprietor is the employer, and the earned-income calculation has to be consistent with the contribution deducted. If you are unsure which of those you are, you are not ready to file a pension deduction today. Extend, if the entity is one that should extend, and put the structural question at the top of the CPA's stack. Fees for the actuary and the administrator are a separate deduction question. They are not added to the funding wire to "make the minimum."

What today is for

If you are filing the entity return today, the contribution you are deducting for 2025 should already be in the trust, and the CPA should have the confirmation. If it is not in the trust, do not guess that a weekend wire will be treated as timely. Ask the CPA before you file the deduction. If you are extending today, file the extension because the pension number or the rest of the return is not ready, and then write down the date the minimum is due and the date the extended return is due. If those dates are the same, write two tasks anyway. If you are a sole proprietor whose original deadline is still a month away, use that month to get the actuary's 2025 range and to stop describing the 2026 benefit limit as if it applied to last year's deduction.

Also look at 2026 while you are in the file. The year is two and a half months old. Pay credits may already be accruing under a formula that a soft quarter cannot support. A prospective amendment still has more room in March than it will have in November. That amendment is not the 2025 deduction, and doing one does not accomplish the other. Compare the structures only if you are still unsure what you adopted. If you adopted a cash balance plan, you are on the funding clock whether or not you find the 401(k) comparison comforting. If you are self-employed and the only participant, the clocks are shorter to explain and just as real.

The people who get this season wrong are rarely confused about the existence of deadlines. They are convinced that one diligent act covers three. They fund the plan and assume the CPA saw the wire. They extend the return and assume funding moved with it. They file Form 5500 in October and assume the September minimum was a draft of the same project. The remedy is unglamorous. Name the job, name the payee, name the year, and name the date. Then do that job on that date.

What to do in the next two weeks

If today's return is being filed, reconcile the deducted contribution to a custodian receipt dated in time, for the 2025 year, in an amount no higher than the certified maximum and no lower than what you are willing to have funded given the minimum. If today's task is an extension, file it, and open a note with two dates: minimum funding September 15, 2026, and the extended due date of this specific return. Add Form 5500 as a third line, July 31, 2026, extendable to October 15, 2026, so it does not hide inside the first two.

Ask the Enrolled Actuary to state the 2025 minimum and the 2025 maximum in one short letter under the 2025 limits. Ask the CPA which of those numbers the return will use, and what proof of deposit they require. Send both answers to the same place if you want the administration coordinated. Two weeks from today the original due date will have passed for calendar-year S corporations and partnerships. The funding clock will not have passed. It will be closer, and it will still be a different job.