Filing Final Income Taxes for a Deceased Person in Idaho

Losing someone you love is hard enough without having to figure out their taxes. But when a person passes away in Idaho, their final income tax return still needs to be filed with both the IRS and the State of Idaho. If you're the surviving spouse, executor, or personal representative handling this responsibility, knowing the correct steps can save you from penalties, delays, and unnecessary stress during an already difficult time.

Who is responsible for filing the final tax return?

The responsibility falls to the personal representative of the estate. This could be an executor named in the will or an administrator appointed by the court. If the deceased had a surviving spouse, the spouse can file a joint return for the year of death. In some cases, a surviving spouse may also need to understand Idaho's probate tax filing requirements before moving forward.

If no personal representative has been appointed and there is no surviving spouse, a person charged with the deceased's property may need to file on their behalf.

What forms do you need to file?

For federal taxes, you'll file the same IRS form the deceased would have used usually Form 1040 covering income from January 1 through the date of death. You'll write "Deceased" and the person's name and date of death at the top of the return.

For Idaho state taxes, you'll use Form 40 (Idaho Individual Income Tax Return). The state treats the final return the same way it covers the tax year up to the date of death.

You may also need to file an Income Tax Return for Estates and Trusts (Form 1041) at the federal level if the estate earns income after the date of death, such as interest, rental income, or dividends. A separate Idaho estate tax filing may apply depending on the estate's value, though Idaho does not currently impose a state-level estate or inheritance tax.

When is the final tax return due?

The final federal and Idaho returns are due on April 15 of the year following the death, just like a regular tax return. For example, if the person died on June 10, 2024, the final return would be due April 15, 2025.

If you need more time, you can file Form 4868 for an automatic six-month extension. But keep in mind: an extension to file is not an extension to pay. Any taxes owed should still be paid by the original deadline to avoid interest and penalties.

What income should be included on the final return?

You report all income the deceased received from January 1 through their date of death. This typically includes:

Wages and salary earned through the date of death
Self-employment income received before passing
Interest and dividends earned through the date of death
Retirement income, including pensions and IRA distributions received before death
Social Security benefits received through the month of death
Rental income received before the date of death
Capital gains on assets sold before death

Any income earned after the date of death belongs to the estate, not the deceased individual. That income gets reported on the estate's tax return (Form 1041) instead.

Can a surviving spouse file jointly?

Yes. If you are a surviving spouse and you did not remarry before the end of the tax year, you can file a joint return for the year your spouse died. This is often the most favorable filing status and typically results in a lower tax bill.

You would sign the return as the surviving spouse and write your spouse's name and "Deceased" at the top. You'll also need to attach a copy of the death certificate in some cases. Filing jointly can affect your eligibility for credits and deductions, so it's worth understanding how it ties into the broader estate settlement process in Idaho.

What documents do you need to gather?

Before you sit down to file, collect these documents:

Death certificate (certified copy)
The deceased's Social Security number
All W-2s and 1099s for the year of death
Prior year's tax return (helpful as a reference)
Records of deductible expenses (medical bills, charitable donations, mortgage interest)
Bank and investment account statements
Letter of Testamentary or court documentation showing your authority as personal representative

You can find more detail on the full list of documents needed to settle an estate in Idaho, which covers tax filing as well as other administrative steps.

How do you file the return with Idaho?

Idaho follows the same general process as the federal return. Here are the steps:

Gather all income documents covering January 1 through the date of death.
Complete Form 40 for Idaho, marking the filer as deceased.
Attach supporting documents, including W-2s, 1099s, and any relevant schedules.
Sign the return as the personal representative, surviving spouse, or authorized filer.
Mail the return to the Idaho State Tax Commission at the address listed on the form instructions, or file electronically if available through your tax software.
Include payment if taxes are owed, or provide direct deposit information for a refund.

Idaho may also require you to submit a copy of the death certificate and documentation proving your role as the personal representative. The Idaho State Tax Commission website provides current mailing addresses and form instructions.

What are common mistakes people make?

Handling a deceased person's taxes is unfamiliar territory for most people. Here are the errors that come up most often:

Filing under the wrong filing status. A surviving spouse qualifies for "Married Filing Jointly" for the year of death. Don't accidentally file as single.
Forgetting to report income earned before death. Check for W-2s, 1099-INTs, 1099-DIVs, 1099-Rs, and SSA-1099 forms. The IRS still expects all of this income to be reported.
Missing the filing deadline. The due date doesn't change because someone passed away. If you're unsure, file for an extension.
Not filing when a refund is due. Even if income was low, there may be a refund available especially from withholding or estimated payments made during the year.
Commingling estate income with the final return. Income earned after the date of death goes on the estate's return, not the individual's final return.
Ignoring Idaho-specific requirements. Federal and state returns are separate filings. Don't assume one covers the other.

What if the deceased owed back taxes?

If the deceased owed taxes from prior years, those debts become an obligation of the estate. The personal representative must address outstanding tax liabilities during the estate settlement process. You may need to negotiate with the IRS or the Idaho State Tax Commission, and unpaid taxes generally take priority over other unsecured debts.

For a broader view of the estate's obligations, review the Idaho estate settlement paperwork guide to understand how tax debts fit into the overall process.

Do you need professional help?

For straightforward situations a surviving spouse filing jointly with simple W-2 income you may be able to handle the final return yourself using tax software or the paper forms. But if the deceased had complex income sources, owned a business, had significant investments, or if the estate is large enough to require a federal estate tax return (Form 706), working with a tax professional or estate attorney is worth the cost.

Errors on a deceased person's return can create problems that follow the estate for years. A CPA familiar with Idaho tax law can help you avoid costly missteps.

Quick checklist for filing final taxes in Idaho

Obtain a certified death certificate
Confirm your authority as personal representative or surviving spouse
Collect all income documents (W-2s, 1099s, Social Security statement)
Complete federal Form 1040 for income through date of death
Complete Idaho Form 40 for income through date of death
File jointly as surviving spouse if eligible
Determine if estate income requires Form 1041
File by April 15 (or request an extension with Form 4868)
Mail Idaho return to the State Tax Commission with supporting documents
Keep copies of everything filed for your records

Tip: Start gathering tax documents early. Waiting for all forms to arrive can take weeks after a death, and some institutions need a death certificate before releasing records. The sooner you begin, the less pressure you'll feel when the deadline approaches.