Locum Ledger | 2025 Tax Filing Extension Deadline, SEP Last Call & More (Oct 2026)

By Locumpedia Editorial

2026-10-08

Locum Ledger is Locumpedia’s monthly column on the money side of locum tenens work: taxes, entity choice, retirement, insurance, and per diem. It’s built with credentialed experts and anchored to primary sources, with commercial relationships disclosed. We explain the rules rather than giving advice.

If you pushed your 2025 return to the fall, the calendar is about to run out. October 15 is the day the paperwork comes due, and it’s also the last day to fund one of the biggest retirement accounts a locum can reach.

The Extended-Filing Deadline

October 15, 2026, is the extended deadline to file a 2025 individual return for anyone who requested an extension back in April. It lands on a Thursday this year, so the deadline won’t shift for a weekend.

An extension gives you more time to file, not more time to pay. Any 2025 balance was due in April. The IRS is explicit that the extra time is for the return, not for what you owe.

SEP Last Call & Solo 401(k) Timing

October 15 is also a retirement deadline, one people can easily miss. A SEP-IRA can be set up and funded through the extended due date of the return, so a locum who filed an extension still has until October 15 to make a 2025 contribution. After that date, the 2025 window closes for good.

The 2025 ceiling is up to 25% of compensation, capped at $70,000, with a lower effective rate once you run the self-employed math. That cap is a 2025 figure. The same limit rises to $72,000 for 2026, but the money going in by this October is measured against last year’s number.

A Solo 401(k) follows different timing. The employer contribution for 2025 can generally be made by the due date, including extensions. An owner-employee’s elective deferral had to be elected by the end of 2025, although special timing rules apply to certain first-year plans. The two accounts look alike on a comparison chart and split apart on exactly the dates that matter, so they’re worth reading side by side rather than assuming they line up.

The Mileage Rate Rose Midyear

The 2026 business mileage rate is not one number this year. It’s 72.5 cents a mile for January through June, then 76 cents from July 1 forward, a midyear bump the IRS set in its July bulletin.

Midyear changes are rare. The last were in 2011 and 2022. For a locum logging miles between assignments, that means eligible business miles from July onward carry a higher standard rate than those logged from January through June. A log that assumes a single 2026 rate will be wrong for half the year.

The standard rate isn’t the only method. The IRS also allows the actual expense method, which tracks the real cost of running the vehicle instead of a flat per-mile figure. The method you choose can affect your options in later years, so it’s one to understand before the first log entry, not after.

Year-End Moves & Next Year’s Numbers

With the extension deadline cleared, the next hard date on the 1099 calendar is January 15, 2027, the fourth-quarter 2026 estimated payment. Taxpayers who expect to owe at least $1,000 after withholding and refundable credits may need to make estimated tax payments.

Fall is also when there’s still time to make current-year retirement contributions. For 2026 the elective deferral limit is $24,500, the age 50 catch-up is $8,000, a larger $11,250 catch-up applies at ages 60 through 63, and the IRA limit is $7,500. The SEP and defined-contribution cap is $72,000.

The 2027 figures aren’t out yet. The IRS usually releases next year’s contribution limits and inflation adjustments in late October or November. And 1099-NEC forms for 2026 work start reaching providers early in the new year, which is when next year’s filing season quietly begins.

What Independent Locum Physicians & APPs Are Weighing This Month

SEP vs Solo 401(k)

Locumstory, the neutral industry resource, runs a side-by-side on the solo 401(k) and SEP-IRA for self-employed physicians, the two accounts October’s deadline puts back in play. Its takeaway is that the solo 401(k) usually offers more contribution room for moderate earners and anyone 50 or older, because it layers an employee deferral on top of the employer contribution.

The Independent Contractor Checklist

The White Coat Investor keeps a financial planning checklist for 1099 contractor physicians that opens with locum work. On retirement accounts, it argues the individual 401(k) is almost always the better fit than a SEP-IRA for an independent contractor physician, since it reaches the maximum on less income and keeps a backdoor Roth workable.

Running the Numbers

Physician on FIRE works the same comparison through 2026 income scenarios, showing where a solo 401(k) reaches the same ceiling at a lower income than a SEP because it stacks an employee deferral on the employer piece. It’s the arithmetic behind the account choice rather than a blanket call.

The Extension Playbook

The Doctor’s CPA, a Locumpedia content contributor, publishes a locum-specific walkthrough of the 2026 filing extension and October 15 filing deadline. It’s a commercial tax practice writing about the deadline it helps clients meet, a relationship readers should keep in mind.

Coverage Gaps

Locum Independence, also a disclosed contributor, looks past taxes at the malpractice coverage mistakes locums make: tail exposure when a claims-made policy ends with the assignment, confusion between claims-made and occurrence coverage, and gaps that open when several assignments carry policies from different carriers. Its argument is that coverage gaps can emerge across assignments if policies aren’t carefully coordinated, and it’s a practice that sells this kind of review, which the disclosure makes plain.

Locum Ledger reports on the tax rules that affect independent physicians and APPs. It describes the rules; it doesn’t tell you what to do with them. This edition draws on reporting from independent and neutral publishers and from The Doctor’s CPA and Locum Independence, Locumpedia content contributors whose commercial relationships are disclosed. Locumpedia is independent and free. No source pays for placement.