S Corporation and Partnership Returns Are Due March 16: Are Your Books Ready?
· RKube Services
2025 Forms 1120-S and 1065 are due March 16, 2026. What's due, how the Form 7004 extension works, and why clean books come first.
If you own an S corporation or a multi-member LLC taxed as a partnership, your business return is due a full month before your personal one. Every year some owners find this out in the second week of March, usually while they're still trying to figure out why the bank balance in QuickBooks doesn't match the bank.
For 2025 calendar-year businesses, Form 1120-S and Form 1065 are due Monday, March 16, 2026. The statutory date, March 15, falls on a Sunday this year.
What's Due on March 16
- Form 1120-S, the S corporation income tax return
- Form 1065, the partnership return
- Schedule K-1s for each shareholder or partner, which have to be furnished to owners by the same date
- Form 7004, if you need more time to file
These are pass-through returns. The business generally doesn't pay federal income tax itself. Instead, income, deductions, and credits flow through to the owners on their K-1s, and the owners report them on their personal returns. That's why the deadline is earlier: owners can't finish their own returns without their K-1s.
Sources: IRS: About Form 1120-S, IRS: About Form 1065
The Extension Option: Form 7004
Filing Form 7004 by March 16 gives an automatic six-month extension, which moves the deadline to Tuesday, September 15, 2026. There's no need to explain why.
An extension is often the right call. If your books aren't done, it's better to file an accurate return in the summer than a rushed one in March that you have to amend later. Keep in mind that the owners will probably need to extend their personal returns too, since their K-1s won't be ready by April 15.
Source: IRS: About Form 7004
What Happens If You Miss It
The late-filing penalty for S corporations and partnerships works differently than most people expect. It isn't based on tax owed, since the entity usually doesn't owe any. It's a flat dollar amount, adjusted for inflation each year, charged per shareholder or partner, per month (or part of a month) the return is late, for up to 12 months.
A three-owner business that files five months late is looking at 15 months' worth of that per-owner charge. It adds up quickly, even when the business made no money. The IRS does offer relief for reasonable cause and, in some cases, first-time abatement, but it's much better not to need it. The current per-month amount is listed in the form instructions.
Why Clean Books Come First
A pass-through return is basically a summary of your books. If the books are wrong, the return is wrong, and so is every owner's K-1. Here's what we most often have to fix before we can prepare a 1120-S or 1065:
- Bank and credit card accounts that haven't been reconciled through December 31
- Owner distributions recorded as expenses, or personal spending run through the business account
- Loans to or from owners that aren't recorded as loans
- Equipment purchases expensed in full with no record of the date or cost
- For S corporations, no owner payroll, or payroll that doesn't line up with the W-2
Those last points matter because the balance sheet is part of the return, and distributions and owner basis affect how much of what an owner took out is taxable.
Example Scenario
An S corporation with one owner reports $412,000 in revenue and books show net income of $96,000. During review we find:
- $38,000 of owner transfers coded as "contract labor" (they were really distributions)
- $6,500 of personal expenses paid from the business card
- A $22,000 equipment purchase from October booked as "supplies"
Reclassifying the transfers and personal charges raises ordinary income by $44,500, to $140,500. Treating the equipment as a fixed asset, and then deciding how to depreciate it, changes the number again. Under current law, qualifying property acquired after January 19, 2025 is eligible for 100% bonus depreciation, but that choice should be made on purpose, not by accident through a miscoded expense. Each of these changes the owner's K-1 and personal return.
None of this is unusual. It just takes time, which is why February is when this work should happen.
How RKube Helps
- We reconcile and close your 2025 books so the return reflects what actually happened
- We prepare Form 1120-S or 1065 and every owner's K-1
- We file Form 7004 on time when an extension makes more sense
- We review owner payroll, distributions, and basis so the K-1s hold up
- We set up monthly bookkeeping so next year isn't a scramble
If your books are behind, you can start a free 30-day bookkeeping trial or call (984) 234-7030 to talk through your timeline.
Final Thoughts
With about four weeks until March 16, you have two good options: get the books finished now and file on time, or file Form 7004 and do it right by September 15. The option to avoid is doing neither. Every business is a little different, so check with a tax professional about which path fits yours.
RKube Services
Bookkeeping, tax preparation, payroll, and proactive tax planning.