You’re ready to file, except you are still waiting on a 1099, a K-1, or you are sorting a year’s worth of travel receipts.
If you worked multiple assignments in multiple states, rushing a return can turn small gaps into expensive mistakes.
A tax filing extension can be a smart move for locum physicians, but only if you pair it with a solid payment estimate. This guide explains what an extension buys you for the 2026 filing season, what it does not, and how to use the extra time to strengthen a multi-state, multi-1099 return.
Extension Basics: What You’re Actually Getting
A federal extension typically gives you about six more months to file your individual return.
For the 2026 filing season, keep these two dates in mind:
- March 15, 2026: Deadline to file S-Corporation or Partnership Extensions
- April 15, 2026: Deadline to file and pay for most individual taxpayers
- September 15, 2026: Final extended deadline for S-Corporations or Partnerships
- October 15, 2026: Common extended filing deadline (when an extension is filed on time)
The core tradeoff is straightforward: an extension gives you more time to file, not more time to pay. If you will owe, your goal is to make a reasonable payment by the original deadline and use the extension window to finalize the return.
If you file an extension on time, you can reduce the risk of a late-filing penalty. That’s valuable when you’re waiting on forms or reconciling multi-state details. But interest and late-payment penalties can still apply if you underpay by April 15, 2026.
What An Extension Does Not Buy You
Locums tend to run into the same three misunderstandings. Here is the reality check.
“I filed an extension, so I’m safe.”
A personal income tax extension does not eliminate interest or late-payment penalties if you do not pay enough by the original deadline. Think of the extension as paperwork breathing room, not a payment pause. To reduce additional penalties and interest on the tax amount due, you must pay the lesser of 90% of your current year’s tax liability or 100% of the previous year’s total tax. For high-income earners (Adjusted Gross Income over $150,000), the requirement is 110% of the prior year’s tax.
“I can ignore planning until October.”
If your income is spiky, waiting until October often leads to an avoidable balance due. A better approach is to estimate what you owe by April 15, 2026, make a payment with your extension, then refine the numbers during the extension window.
“An extension fixes missing recordkeeping.”
An extension buys time, but you still need to use that time to reconcile income, document expenses, and allocate income across states. If you have no system at all, the extension can simply delay the problem and increase the cost.
What’s the Best Way to File a 2026 Personal Tax Extension?
There are two common ways to request an extension. Choose the route that matches how you want to document your request.
Option A: file form 4868
You (or your locum tenens CPA) can e-file Form 4868. If you expect to owe, include a payment with the extension to reduce interest and penalty exposure.
Option B: pay electronically and mark it as an extension payment
An electronic payment can function as your extension request when you designate it as an extension payment. This approach is popular because it creates a clear payment record and confirmation.
If you expect a refund, you can still extend. Just remember the tradeoff: delaying filing can delay your refund.
If your electronic extension filing doesn’t go through, you can file a paper extension. The form must be completed in its entirety and certified mailed with tracking to ensure timely filing with a copy of your electronic extension payment or a check made payable to the US Treasury.
Note: Locum physicians who receive income through an entity filing as a Partnership or an S-Corporation must file Form 7004 for an extension.
When Does an Extension Make Sense For Locum Physicians?
A general-audience extension article rarely addresses the real locum problem: variable income plus multi-state filing complexity.
Smart reasons to extend
An extension is often reasonable when you need more time for one of these situations:
- Late or corrected tax documents (multiple 1099s, a K-1, brokerage forms)
- Multi-state allocations that require careful review
- Reconciling income across multiple payers when deposits do not match forms yet
- Finalizing deductions that depend on clean documentation (travel, licensing, CME)
- Strategizing for retirement contributions, including employer matching, profit share, and/or cash balance plans
Red flags that signal a bigger issue
An extension is a warning sign when it is being used to cover for missing fundamentals. For example, you may need help sooner if you:
- Are months behind on bookkeeping
- Have not tracked expenses at all
- Cannot produce even a rough estimate of taxes owed
In these cases, the best move is not “extend and hope.” It is “extend and build a plan.”
A Practical Pre-Extension Checklist
Before you extend, aim to get to “good enough to estimate.” You do not need perfect numbers, but you do need a defensible process.
Start with these items:
- All 1099-NECs received so far, plus any pay statements or agency summaries
- A year-to-date income total by payer (spreadsheet is fine)
- Mileage and travel records tied to assignments
- Licensing, credentialing, CME, DEA, and professional dues
- A list of states worked in, with approximate dates and earnings by state
- A copy of the prior year’s personal income tax return
If you are missing something critical, approximate conservatively and document how you got there. Examples:
- If a 1099 is missing, use bank deposits and payer statements to estimate gross income.
- If mileage logs are incomplete, reconstruct from your calendar, assignment dates, and maps, then tighten the log during the extension window.
- If expenses are uncategorized, export transactions and tag the obvious business items first. Leave a “needs review” bucket for items you and your CPA will verify later.
How to Estimate What You Owe Without Perfect Numbers
Locum estimation is less about precision and more about avoiding the two worst outcomes: paying nothing when you owe a lot, or ignoring state and self-employment taxes.
Use this simple framework:
- Total your income (all 1099s received plus best estimates for missing forms)
- Subtract known business expenses (use conservative amounts when unsure)
- Use your prior-year effective tax rate as a starting point, then adjust if this year’s income changed materially
- Account for self-employment tax if you are paid as a 1099 contractor
- Add state tax estimates for the states where you worked
- Subtract what you have already paid (withholding, estimated payments, prior credits)
- Pay with your extension by April 15, 2026, to reduce interest and late-payment penalty exposure
Avoid These Common Errors Locum Physicians Often Make
Most extension headaches come from a short list of misses:
- Forgetting self-employment tax
- Ignoring state taxes in work states
- Mismatching 1099s (if any) to your deposits
- Misclassifying travel (especially when personal travel is mixed in)
- Mixing business and personal spending, then trying to sort it out at the end
Use the Extension Window to Strengthen Your Return
If you extend, decide what “done” looks like and work backward from the October deadline. Most locums get the best results when they use extension time to:
- Match each payer’s totals to deposits and confirm no income is missing
- Clean up expense categories and attach support for major deductions
- Finalize multi-state allocations with clear state-by-state income estimates
- Review estimated tax habits so next year is not another April scramble
Frequently Asked Questions
Does a tax filing extension reduce my tax bill?
No. An extension changes the filing deadline, not the amount you owe. Your tax is based on your income and deductions for the year.
Can I file an extension if I think I’ll get a refund?
Yes, but filing later often means receiving the refund later.
Does an extension replace quarterly estimated taxes?
No. Quarterly estimated taxes are a separate habit that helps prevent underpayment. An extension does not “pause” good estimated tax planning.
Official Resources (For Filing And Payments)
Use primary sources when possible:
- IRS newsroom: Extension to file is not an extension to pay
- Form 4868 (official form and instructions)
- IRS Direct Pay (extension payments)
- CFPB: 2026 guide to filing your taxes
Need help estimating what to pay with your extension and tightening up your locum deductions? Talk to The Doctor’s CPA about extension planning and locum-specific tax strategy.