You can e-file a return up to six months past the due date. After that, you must mail the return. If you’re filing multiple years, most older returns need to be submitted manually.
- Order of Filing: The IRS does not require missing tax returns to be filed in strict chronological order, and they do not specifically check to see if you filed them in order. While the IRS prefers chronological order, the most important priority is to file all missing returns, particularly if you are in a "good standing" situation requiring the last six years.
- Why Order Matters: Failing to file in order can cause issues with IRS processing, especially if a return for an earlier year affects the balance of a later year. Filing in order ensures that carry-forward items—such as net operating losses, capital losses, or unused tax credits—are accurately reflected on subsequent years' returns.
If your nephew's returns are simple, these carry-forward issues may be moot.
What I would do: I'd complete the 2024 return, keep a copy (so you have its data for 2025 if needed), and mail it so you don't forget. Then prepare the 2025 (using any needed 2024 data) and try to e-file. In order to ID your nephew, you'll probably be asked to enter the 2024 Adjusted Gross Income (AGI). Since they have not processed 2024 for him, try entering $0 for the AGI and see if it flies. If not, print and mail it.
