Key takeaways
- The state return is Form S-Corp, the New Mexico Sub-Chapter S Corporate Income and Franchise Tax Return, due on or before the federal due date.
- A federal extension is recognized, but an extension to file does not extend the time to pay.
- The entity-level tax election is made annually on the return and binds every owner.
- Nonresident owners are either withheld on or covered by the election, and that choice comes before the return is prepared.
Which New Mexico return an S corporation files
A corporation with a valid federal S election files Form S-Corp, titled New Mexico Sub-Chapter S Corporate Income and Franchise Tax Return. Do not prepare Form CIT-1 for it. CIT-1 is the C corporation return, and the confusion starts because the Department's overview describes CIT-1 as the form reporting the annual franchise tax and says franchise tax reaches S corporations.
The Department's pass-through page also lists Form PTE and FID-1. Those are for entities that do not file a federal corporate return, such as partnerships and certain trusts. If a prior-year file shows an S corporation on Form PTE, check the federal return type and ask the client what happened.
The franchise tax is a flat annual amount that the Department describes as $50, and it is owed whether or not income tax is due. Confirm the amount and line in the Form S-Corp instructions for the year, since the overview page points to CIT-1 for that figure.
Due date and extension for tax year 2026
The Department says to file on or before the due date of the federal return. Form 1120-S is due the 15th day of the third month after year end. For a calendar-year S corporation, the 2026 return is therefore due March 15, 2027, a Monday, so no weekend shift applies. For 2025 returns the IRS instructions give March 16, 2026, because March 15 fell on a Sunday.
A federal extension is recognized. The Department states that if you obtained a federal automatic extension you do not need a separate New Mexico application. Form 7004 is the federal request and gives an automatic six months. File it by the regular due date and keep the confirmation in the client folder.
Payment is where firms get caught. The Department states that an extension of time to file does not extend the time to pay, and interest runs from the original due date. If the client owes entity-level tax, estimate it and pay by the original due date even though the return is not ready. The estimated payments do not have to be quarterly, so a single payment in March works.
If the entity did not obtain a federal automatic extension, New Mexico uses Form RPD-41096, and the Department says initial extensions are typically granted for 60 days. An entity with a federal extension needs no separate New Mexico application, and the guide should not promise time beyond the federal extended due date.
Entity-level tax: the PTE election
The entity elects by filing its New Mexico return and completing the entity-level tax section. There is no separate election form. The Department says the election is binding on all owners, is made each year, and cannot be changed by an amended return.
The tax is figured at the higher of the personal or corporate rate, and the Department states the highest rate for both is currently 5.9%. The election replaces withholding for the owners it covers. The entity gives each owner RPD-41359, which the owner uses to claim a credit on their own return. RPD-41359 is not filed with the Department.
Some owners cannot be covered. The entity may not pay tax for an owner that is a government body, a federally recognized tribe, a 501(c)(3) organization, a corporate partner that includes the income in its unitary business income, or a pass-through entity owner. For an S corporation, a tax-exempt shareholder is the case to look for. Check the shareholder list against this before you promise the client a flat answer.
The Department also says entities with net operating losses should not elect at present. So model the election in November, not in March. If the entity has a state loss carryforward, the answer is usually no. If every shareholder is an individual and the client wants nonresident owners spared a separate filing, run both numbers and let the client choose.
Nonresident shareholders: withholding and composite
The entity must withhold on each nonresident owner's share of net income, unless it elected entity-level tax and paid for that owner. For tax years starting in 2023, withholding is reported and paid on the entity's own return, Form S-Corp here. For tax year 2022 and earlier it was RPD-41367, so work papers built on that form are out of date.
The Department's pass-through page does not state a withholding percentage. Do not carry a rate over from an older instruction sheet or a blog. Read the percentage from the Form S-Corp instructions for the tax year and note the instruction version in the work papers.
A composite return is the other route. Section 7-3-14 NMSA 1978 lets the entity file a composite return for electing nonresident members whose only New Mexico income comes from pass-through entities. The entity pays at the highest marginal rate on their New Mexico share. A nonresident who also has New Mexico wages or rental income does not fit.
Decision rule for each nonresident shareholder: if the S corporation is the only New Mexico income, ask whether the owner wants to be in the composite. If the owner has other New Mexico income, the owner files their own return and is either covered by the election or withheld on. Get the answer in writing before preparing the return.
Penalties and e-filing
The federal late filing penalty on Form 1120-S drives timing. The IRS charges $255 for each month or part of a month, up to 12 months, times the number of shareholders, for returns required to be filed in 2026. A three-shareholder company filing four months late owes $255 times 3 times 4, which is $3,060. Check the 2026 instructions for the adjusted amount that applies to the 2027 season.
Tax due adds 5% of the unpaid tax per month, up to 25%. No New Mexico penalty figure is quoted here because the Department's pass-through pages do not give one.
E-filing is required if the entity has more than 50 payees. A paper-filing exception is requested with RPD-41350.
What to collect from the client
Send one request by the end of January. Wording that works: "For the New Mexico return we need the shareholder list with each person's state of residence on December 31, a note of which owners have New Mexico income other than the company, and your decision on the entity-level tax election." The reply date goes in the same message.
From the books, pull the Form 1120-S work papers, the apportionment inputs (payroll, property and sales by state if the company operates outside New Mexico) and any state loss carryforward. From the client, get the prior-year Form S-Corp, any prior RPD-41359 statements and state franchise tax correspondence.
For each shareholder, collect name, taxpayer ID by secure upload, address, state of residence, owner type (individual, trust, estate or exempt organization) and other New Mexico income. If a shareholder moved during the year, ask for the move date.
Keep the election decision, the residency answers and the extension confirmation in one folder, because a reviewer or a notice will ask for those three. In Usual, one request can hold the shareholder questions and secure upload fields, with reminders until the client finishes.
Failure modes and fixes
The most common error is preparing CIT-1 because the franchise tax overview mentions it. Key the state return off the federal return: Form 1120-S gets Form S-Corp, Form 1120 gets CIT-1, Form 1065 gets Form PTE.
The second is a late S election. If a corporation never filed Form 2553 or filed it late, the IRS says it may be entitled to relief. Resolve that first.
The third is treating the election as reversible. Because an amended return cannot change it, a client who elects and then learns an owner could not be covered has no clean exit. Walk the owner list before signing and keep the signed decision in the file.