Idaho Bonus Depreciation: Conforms Today, But Not on Autopilot.
Idaho conforms to federal §168(k) bonus depreciation through a fixed conformity date the legislature re-sets every session — currently the Code as of January 1, 2026, which captures the restored 100% bonus. That is not the same guarantee as rolling conformity, and this page explains why.
Reviewed by Cost Seg Smart Editorial Team · Last verified against Idaho Code §63-3004 — Internal Revenue Code definition
The 30-second answer: Idaho conforms to federal §168(k) bonus depreciation today. Idaho Code §63-3004 defines the adopted Internal Revenue Code as of a fixed date, currently January 1, 2026, with no exception for §168(k) — and that date sits after OBBBA, so the restored 100% bonus flows through for both individuals and businesses.
This is NOT rolling conformity. The legislature has to re-set that fixed date every session. If a future session does not move it forward, Idaho's federal reference freezes and would lag behind any new federal depreciation change enacted after that point — worth re-checking each year rather than assumed permanent.
On a representative Idaho single-family rental (the single-family rental band we publish, 9–32% of depreciable basis reclassified, 16% representative), the reclassified components alone generate an estimated $18K–$165K of federal Year-1 depreciation — roughly $6,660–$61,570 of Year-1 tax savings at the 37% top bracket, flowing through identically on the current Idaho return.
Federal vs Idaho, Side by Side
For an individual investor's or Idaho business's cost-segregation-reclassified components:
| Tax provision | Federal (IRC) | Idaho |
|---|---|---|
| Bonus depreciation under §168(k) | 100% may apply to qualified property acquired and placed in service after January 19, 2025, subject to §168(k) eligibility, related-party/prior-use, binding-contract, and election rules | Flows through today. Idaho adopts the Code as amended and in effect 2026-01-01, no §168(k) exception (Idaho Code §63-3004) |
| Conformity mechanism | Not applicable | Fixed date, re-set annually by the legislature — not rolling conformity |
| Other exceptions to conformity | Not applicable | Only §85 and a §174 timing rule are frozen to other dates — §168(k) has no such carve-out |
| Individual vs business | Same §168(k) rules for both | Same section, no taxpayer-type split |
| Federal usability of the deduction | Subject to passive activity, at-risk, basis, and business-interest limits | Same federal limits govern the federal deduction; Idaho adds no state-level reduction while conformity holds |
Sources: Idaho Code §63-3004, IRC §168(k). Federal bonus figures reflect current law; eligibility depends on acquisition and placed-in-service dates and elections.
Fixed date, not rolling — the distinction that matters
Some conforming states track the Internal Revenue Code automatically as it changes — "rolling conformity." Idaho is not one of them. Idaho Code §63-3004 defines the adopted Code as of a fixed date that the legislature must affirmatively re-set every session, currently January 1, 2026. Today's outcome is favorable: that date falls after the One Big Beautiful Bill Act and its January 19, 2025 retroactive effective date, so Idaho currently captures the restored 100% federal bonus.
But the mechanism itself carries a structural risk worth naming directly: if a future legislative session does not update the reference date, Idaho's conformity freezes wherever the date was last left, and any new federal depreciation change enacted after that point would not automatically apply in Idaho until the legislature acts again. Nothing about today's favorable result changes that dependency.
For a property owner or CPA, the practical takeaway is to re-verify Idaho's current conformity date each filing season rather than assume today's answer carries forward automatically. Only two other provisions — §85 and a §174 timing rule — are frozen to different dates in the same section; §168(k) itself has no separate carve-out and simply follows the general fixed date.
Illustrative numbers: an Idaho single-family rental
Using the single-family residential (SFR) band we publish — 9–32% of depreciable basis reclassified into 5/7/15-year property, 16% representative — on a property priced between $250,000 and $650,000, with a 20% residential land allocation, and 100% federal bonus depreciation for eligible components under current law and Idaho's current conformity date:
| Line item | Federal | Idaho |
|---|---|---|
| Purchase price band | $250,000–$650,000 | Same property |
| Depreciable basis (20% land allocation) | $200,000–$520,000 | Same basis |
| Reclassified to 5/7/15-yr (9–32% of basis) | $18K–$165K | Same reclassification, same components |
| Year-1 treatment | $18K–$165K deducted (100% bonus, if eligible) | Same $18K–$165K deducted — Idaho follows the federal figure while conformity holds |
| Marginal tax rate | Up to 37% | Idaho individual income tax rate (verify current year with the Idaho State Tax Commission) |
| Illustrative Year-1 federal tax savings on reclassified components | ~$6,660–$61,570 (37% × $18K–$165K) | Same deduction reduces Idaho taxable income today; re-verify each year |
Figures are illustrative and use the site's published SFR reclassification band; your result depends on your basis, land allocation, bracket, component mix, and eligibility. Whether the full federal deduction is usable in the current year still depends on your passive-loss, at-risk, basis, and business-interest situation. Idaho's conformity date is set by the legislature each session — confirm it has not lagged before relying on this table in a future filing year.
See a sample cost segregation report
Look at exactly what your Idaho study delivers: the component-by-component 5/7/15-year schedule, the Form 4562-ready numbers, and the documentation your CPA files. Real reports are our best answer to "is this legit?"
Forms your CPA files for an Idaho property
For an Idaho investor or business, the depreciation workflow follows the federal figure directly while Idaho's conformity date remains current:
- Federal Form 4562: depreciation and amortization, including the §168(k) bonus deduction on eligible reclassified components. Flows to Schedule E (rental) or Schedule C (active business).
- Schedule E (or Schedule C): the accelerated federal deduction reduces federal taxable income in Year 1, subject to the federal passive-loss, at-risk, basis, and business-interest limits.
- Idaho income tax return: Idaho taxable income starts from the federal figure computed under the Code as of Idaho's current conformity date, currently 2026-01-01 — no separate add-back for §168(k).
- Form 3115 §481(a) section: included only if this is a federal lookback method change on a property placed in service in a prior year (see below).
The reclassified schedule is the same engineered output for both books; Idaho simply follows the federal number, contingent on the legislature keeping the conformity date current.
Form 3115 lookback on an Idaho property
If the property was placed in service in a prior tax year and depreciation was reported using a non-segregated method, a federal Form 3115 (Application for Change in Accounting Method) may allow a current-year §481(a) catch-up adjustment for the accelerated depreciation you missed, generally without amending prior returns. This is often the single biggest acceleration mechanism in cost segregation. Any catch-up dollars are illustrative and depend on placed-in-service date, prior depreciation claimed, bonus eligibility, land allocation, and component mix.
The federal §481(a) catch-up is the primary lever, and it remains subject to the federal passive-loss, at-risk, and basis limits. For Idaho, the catch-up flows through to the Idaho return the same way as an ordinary Year-1 bonus, provided Idaho's conformity date in the catch-up year is current with the federal provision being claimed.
See our full Form 3115 cost segregation guide for federal mechanics, partnership and LLC pass-through treatment, and timing rules.
Should you skip cost segregation in Idaho? No.
Idaho's current conformity captures the full federal benefit with no state-level reduction. The math favors doing the study, for three reasons:
- Idaho follows the federal figure today. The fixed conformity date currently sits at 2026-01-01, after OBBBA, so the restored 100% bonus flows through on both returns. How much you use in the current year still depends on your passive-loss, at-risk, basis, and business-interest situation.
- The Form 3115 lookback still captures missed federal years. If the property was placed in service in a prior year and depreciated without cost segregation, the federal §481(a) catch-up may be available, generally without amending prior returns.
- The state-tax picture is genuinely simple today. No add-back, no subtraction schedule, no manufacturing carve-out — the reclassified schedule applies identically on both returns while conformity holds.
The nuance to flag with your CPA is not about this year's answer but about next year's: Idaho's fixed-date conformity mechanism depends on the legislature acting again each session, so a study delivered today should have its state treatment re-verified in any later filing year rather than assumed to carry forward automatically.
Frequently asked
Does Idaho allow bonus depreciation?
Yes, currently. Idaho Code §63-3004 defines the Internal Revenue Code by reference to a fixed date that the legislature resets each session — currently the Code as amended and in effect January 1, 2026, with no exception carved out for §168(k). Because that date falls after the One Big Beautiful Bill Act (OBBBA) and after its 2025-01-19 retroactive effective date, Idaho currently captures the restored 100% federal bonus (subject to §168(k) eligibility, related-party/prior-use, binding-contract, and election rules) for both individuals and businesses.
Is Idaho a rolling-conformity state?
No — and this distinction matters more than it sounds. Idaho does NOT automatically track the Internal Revenue Code as it changes; it conforms via a FIXED date, currently 2026-01-01, that the legislature must affirmatively re-set at the start of each session. Today's answer is favorable because the legislature already moved the date past OBBBA. But calling Idaho "rolling conformity" would overstate the guarantee: if a future session does not update the date, Idaho's federal reference freezes at whatever date is last on the books, and any new federal change enacted after that date would not automatically flow through.
What would it take for Idaho to fall behind on bonus depreciation?
A single legislative session that does not pass its usual conformity update. Idaho's fixed-date mechanism depends on affirmative legislative action every session to move the reference date forward. Nothing in §63-3004 updates itself; if the date is left where it is while Congress enacts a new depreciation change, Idaho would be conforming to a Code that predates that change until the legislature acts again. This is a structural risk worth re-checking each year, not a one-time verification.
Are there any exceptions to Idaho's conformity for depreciation-related provisions?
Only two carve-outs were found in this review, and neither touches bonus depreciation: §85 and a §174 timing rule are frozen to other, different dates. §168(k) itself carries no exception in Idaho Code §63-3004, so it follows the general fixed conformity date like the rest of the adopted Code.
Does this apply the same way to individuals and businesses in Idaho?
Yes. The Internal Revenue Code definition in §63-3004 governs the entire Idaho income tax chapter, with no taxpayer-type split. An individual and a business both get the federal bonus deduction exactly as it stands at whatever the current conformity date is.
Is cost segregation still worth it in Idaho?
Yes. Idaho currently conforms to the restored 100% federal bonus with no add-back, so a cost-segregation-reclassified component gets the same accelerated deduction on both the federal and Idaho returns today. The one thing worth tracking with your CPA is Idaho's conformity date itself each filing season — not because today's answer is in doubt, but because the mechanism that produces it depends on the legislature acting again next session and the year after.
Can I use Form 3115 on an Idaho property I bought years ago?
Often, yes, at the federal level. If the property was placed in service in a prior tax year and depreciation was reported using a non-segregated method, a federal Form 3115 (Application for Change in Accounting Method) may allow a current-year §481(a) catch-up for the accelerated depreciation you missed, generally without amending prior returns. Any catch-up dollars are illustrative and depend on placed-in-service date, prior depreciation, bonus eligibility, land allocation, and component mix. Because Idaho currently conforms to the Code as of 2026-01-01, the catch-up flows through to the Idaho return the same way it does federally — subject to Idaho's conformity date remaining current in the year the catch-up is claimed.