How to File the Montana FID-3 Fiduciary Income Tax Return Without a CPA

Filing the Montana FID-3 fiduciary income tax return without a CPA is possible for most executors managing straightforward Montana estates — but the 2024 legislative overhaul completely rewrote the calculation rules, and most commercial tax software has not caught up. If you use TurboTax or H&R Block to prepare the FID-3 without manually verifying the Montana-specific Schedule I and Worksheet I, you risk filing incorrect state tax calculations. This guide explains what triggers the FID-3 requirement, what changed in 2024, and how to complete the return accurately — with or without tax software.

Does Your Estate Even Need to File a FID-3?

The Montana FID-3 is only required if the estate meets both of these conditions:

1. The estate has a federal Form 1041 filing requirement (meaning the estate earned more than $600 of gross income during the tax year)
2. The estate has positive Montana taxable income after applying the 2024 Montana-specific additions and subtractions — OR the estate is a nonresident estate with income from Montana sources

A "resident estate" under Montana law is any estate where the decedent was domiciled in Montana at the time of death. If the decedent lived in Montana and the estate earned even one dollar of bank interest, a rental payment, a dividend, or a capital gain from selling estate property before distribution — the FID-3 is required.

What does not trigger the FID-3: the inheritance itself is not taxable income. Beneficiaries receiving distributions of estate principal do not owe Montana income tax on those distributions. But the estate owes income tax on the money it earned while holding those assets.

What the Estate Must Have Before Filing

Before you open the FID-3, confirm these items are in place:

• Federal Employer Identification Number (EIN) for the estate — not the decedent's Social Security Number. Apply free at irs.gov/businesses/small-businesses-self-employed/apply-for-an-employer-identification-number-ein-online
• Completed federal Form 1041 for the same tax period — the Montana FID-3 starts from federal adjusted total income, then applies Montana-specific modifications
• Montana Form K-1 (FID-3) for each beneficiary who received a distribution — their share of income is allocated on Schedule K-1 and must be reported on their own individual Montana returns
• Documentation of all estate income organized by type: ordinary income (interest, dividends, rents) and net long-term capital gains, because Montana taxes these at different rates

What Changed in 2024 — The Critical Updates

The 2024 Montana fiduciary income tax overhaul made fundamental changes that break any reliance on prior-year returns as templates:

Elimination of the federal tax deduction. Before 2024, Montana fiduciaries could deduct the federal income taxes the estate paid, reducing state taxable income. This deduction no longer exists. The state and federal liability calculations now diverge significantly — Montana taxable income is generally higher than it was under the old rules for any estate that owed federal tax.

Completely redesigned Schedule I. The new Schedule I determines Montana-specific additions to and subtractions from federal adjusted total income. The line items, labels, and calculation sequence are different from prior years. Prior-year returns are not a reliable template.

New Worksheet I. Worksheet I now determines how to allocate the Montana additions and subtractions across beneficiaries' Schedule K-1 forms. This is an entirely new document that did not exist in prior-year filings.

New tax brackets. Ordinary fiduciary income up to $21,100 is taxed at 4.7%. Ordinary income above $21,100 is taxed at 5.9%. Net long-term capital gains are taxed at either 3.0% or 4.1%, depending on the fiduciary's total non-capital gain taxable income.

The critical practical problem: as of 2024, many commercial tax software programs were not updated to reflect Montana's new Schedule I and Worksheet I. The software may appear to calculate a Montana result, but the underlying calculation skips or misapplies the Montana-specific adjustments. The Montana Department of Revenue's own instructions assume you understand what changed from the prior system — they do not provide a plain-English comparison.

Step-by-Step: How to File the Montana FID-3

Step 1: Determine the estate's tax year. An estate may use either a calendar year (January 1 – December 31) or a fiscal year (any 12-month period ending on the last day of a month other than December). The fiscal year can be more advantageous for timing income recognition across beneficiaries. The first return must indicate which year is elected.

Step 2: Complete federal Form 1041 first. The Montana FID-3 begins with federal adjusted total income from Form 1041. Complete the federal return first to establish the baseline. The federal return reports gross income, deductions, and distributions — the Montana return then modifies these figures.

Step 3: Apply Montana Schedule I additions and subtractions. Using the current Schedule I (2024 version), identify all Montana-specific adjustments to federal adjusted total income. These include:

• Interest income on U.S. government obligations (subtracted from Montana income — exempt from state tax)
• Income that was taxed by another state (may be subtracted with credit computation)
• Any Montana-sourced income not captured in the federal figures

Manually confirm each line of Schedule I against the current Montana Department of Revenue FID-3 instructions. Do not rely on software output alone.

Step 4: Apply Montana Worksheet I for beneficiary allocations. If the estate distributed income to beneficiaries during the year, Worksheet I allocates the Montana additions and subtractions among the estate and each beneficiary in proportion to their distributions. Each beneficiary receives a Schedule K-1 (FID-3) showing their share, which they report on their own Montana individual income tax return.

Step 5: Calculate the tax. Apply the current Montana tax rates to the estate's share of taxable income:

• 4.7% on ordinary taxable income up to $21,100
• 5.9% on ordinary taxable income above $21,100
• 3.0% or 4.1% on net long-term capital gains (depending on ordinary income level)

Step 6: Check estimated tax payments. Montana provides an automatic six-month extension for filing the FID-3 (moving the deadline from April 15 to October 15 for calendar-year estates). The extension is for filing only — not for payment. If the estate owes tax, estimated tax must be paid by April 15. Late payment accrues penalties and daily interest.

Step 7: File and pay. File Form FID-3 with the Montana Department of Revenue. Payment can be made via the Montana TransAction Portal (TAP), ACH Credit, or check with the Estate or Trust Tax Payment Voucher.

Common Errors That Create Liability

Filing FID-3 using outdated software without verifying Schedule I. Software that has not implemented Montana's 2024 changes produces an incorrect state result. Verify every line of Schedule I against the current Department of Revenue instructions before filing.

Using the decedent's Social Security Number. The estate is a separate taxable entity from the decedent. Use only the estate's EIN on the FID-3. Using the SSN causes administrative problems with the Department of Revenue.

Missing the estimated tax payment deadline. The extension moves the filing deadline, not the payment deadline. Executors who file on extension and pay with the return — instead of by April 15 — owe penalties and interest on any underpayment.

Confusing inherited principal with estate income. Inherited assets themselves are not taxable to beneficiaries — but income earned by the estate on those assets before distribution is taxable, and must be reported on the FID-3.

Distributing assets before completing FID-3. The estate's tax liability is a creditor claim against the estate that must be paid before final distribution. Distributing estate assets before settling the FID-3 liability creates personal liability risk for the executor.

When to Use a Montana Estate Tax Guide Instead of Relying on Software Alone

Commercial tax software handles federal Form 1041 reliably. The gap is the Montana FID-3's 2024 changes — Schedule I, Worksheet I, and the new rate structure. A Montana-specific guide that explicitly covers these changes lets you use software for federal calculations while applying the Montana-specific layer correctly on top.

The Montana Final Tax & Estate Tax Guide covers the FID-3 overhaul in detail, including the eliminated federal tax deduction, the new Schedule I line-by-line, and the Worksheet I allocation mechanics. It also covers the full filing sequence — how the FID-3 interacts with the final Form 2, the creditor notice window, and the distribution timeline — so the fiduciary return does not get filed out of order.

Who This Approach Is For

• Executors who are comfortable working from instructions and checking their work against official Department of Revenue guidance
• Personal representatives managing estates that earned investment income, rental income, or capital gains from selling estate property
• Surviving spouses who received a Form 1099 after the date of death and are trying to understand why estate income tax is owed when Montana has no estate tax
• Executors who intend to use a CPA but want to understand what the FID-3 requires before the meeting, in order to reduce billable hours

Who This Approach Is NOT For

• Estates with a business that generated complex operating income, depreciation, or multiple income streams requiring professional judgment
• Fiduciaries managing a fiscal-year estate with income allocated across multiple tax years who need actuarial calculations
• Executors where the decedent held property in multiple states and the FID-3 requires nonresident income sourcing rules from other jurisdictions
• Any estate where the decedent and their spouse previously lived in California, Washington, or Texas and may qualify for the community property double step-up in basis — that calculation requires a CPA familiar with the Uniform Disposition of Community Property Rights at Death Act

Frequently Asked Questions

What is the Montana FID-3 deadline?

For calendar-year estates, the FID-3 is due April 15. An automatic six-month extension moves the filing deadline to October 15. Payment is still due April 15 regardless of extension.

What tax rate applies to estate income in Montana?

Ordinary income is taxed at 4.7% on the first $21,100 and 5.9% above that threshold. Net long-term capital gains are taxed at 3.0% or 4.1% depending on the fiduciary's total non-capital gain taxable income.

Does every estate in Montana have to file FID-3?

No. The FID-3 is required only when the estate has gross income above $600 (triggering a federal Form 1041 requirement) and has positive Montana taxable income. Small estates that close quickly without generating post-death income may not trigger the FID-3 at all.

Can I use TurboTax for the Montana FID-3?

TurboTax handles federal Form 1041. Its Montana FID-3 module may not correctly implement the 2024 overhaul — specifically the new Schedule I and Worksheet I. If you use TurboTax, manually verify the Montana-specific additions and subtractions against the current Department of Revenue instructions before filing.

Do beneficiaries owe Montana income tax on what they inherit?

The inherited principal itself is not taxable. But if the estate distributed income it earned during administration — interest, dividends, rents, capital gains — that income is reported on the beneficiary's Schedule K-1 and is taxable on their individual Montana return. Inherited retirement accounts (401k, IRA) are taxed as ordinary income when the beneficiary withdraws funds.

What happens if I distribute estate assets before filing the FID-3?

The estate's tax liability is a valid creditor claim that must be satisfied before assets are distributed to heirs. Distributing before settling the FID-3 liability can create personal financial liability for the executor — the IRS and the Montana Department of Revenue pursue the executor, not just the estate, for unpaid fiduciary taxes.

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