100% Bonus Depreciation Is Back: How Small Businesses Combine Section 168(k) and Section 179 in 2026 to Write Off Equipment the Year They Buy It

Imagine spending $180,000 on a new bakery oven, a delivery van, and a server rack in October — and deducting every penny of it on the return you file next April. No five-year wait. No splitting the cost across half a dozen tax years. No prorating because you bought it in the fourth quarter. Just one big number on the depreciation schedule and a much smaller check to the IRS.

That is the math that came back to life on January 20, 2025, and it is now the default rule for almost every piece of equipment a small business buys in 2026.

The One Big Beautiful Bill Act (OBBBA) permanently restored 100% bonus depreciation under Section 168(k) for property acquired and placed in service after January 19, 2025. The phase-down schedule that was eating into first-year write-offs — 80% in 2023, 60% in 2024, 40% for early 2025 — is over. At the same time, Section 179 got a bigger deduction limit ($2,560,000 in 2026) and a higher phase-out threshold ($4,090,000). Used together, these two provisions are the most powerful tools small businesses have to convert capital expenditures into immediate tax savings.

This guide walks through how the two elections actually work in 2026, why you almost always need to use both, the traps that quietly disqualify property, and a decision framework you can apply before you sign a purchase order.

What Changed on January 20, 2025

For five years, accountants had to talk small business owners off a ledge every fall. "Yes, you can deduct that backhoe — but only 60% of it this year. The rest stretches over the next five." The Tax Cuts and Jobs Act of 2017 had set up a phase-down of bonus depreciation, starting from 100% in 2017–2022 and dropping 20 percentage points each year until it hit zero in 2027.

OBBBA killed the phase-down and made the 100% rate permanent for qualified property acquired and placed in service after January 19, 2025. IRS Notice 2026-11 then walked through how the new rules interact with existing regulations: most of the framework stayed the same, but the trigger date moved from September 27, 2017 to January 19, 2025.

The practical upshot is straightforward:

• If you signed a written binding contract for equipment on or before January 19, 2025, the old phase-down still applies (40% for property placed in service in early 2025).
• If you signed after January 19, 2025, you generally get 100% bonus depreciation, regardless of when the property is delivered.
• New or used property both qualify — as long as it is the first time you used it.

How Section 168(k) Bonus Depreciation Works in 2026

Bonus depreciation is automatic. If your asset qualifies, you take 100% of its depreciable basis as a first-year deduction unless you affirmatively elect out (which most businesses won't, but some should — more on that below).

What qualifies as bonus-eligible property:

• Tangible personal property with a MACRS recovery period of 20 years or less. That covers virtually everything a small business buys: computers, machinery, office furniture, restaurant equipment, manufacturing tools, vehicles, agricultural equipment, and most software.
• Qualified Improvement Property (QIP) — interior improvements to nonresidential real property made after the building was first placed in service, with a 15-year recovery period. Note that exterior work, building enlargements, elevators, escalators, and structural framework are excluded and stay on the 39-year schedule.
• Certain film, television, theater, and qualified sound recording productions.
• Used property is eligible, provided you (or a predecessor) did not previously use it.

What does not qualify:

• Real property (buildings themselves, land improvements with longer recovery periods).
• Property used predominantly outside the United States.
• Property used by tax-exempt organizations or governmental units in a way that disqualifies it.
• Property required to be depreciated under the Alternative Depreciation System (ADS).

No dollar cap and no income limit. This is the killer feature. Section 179 has both. Bonus depreciation does not. A startup spending $4 million on a clean-room build-out can deduct the qualifying portion in full — even if doing so creates a net operating loss the company can carry forward.

How Section 179 Still Matters

If bonus depreciation is now 100% with no cap, you might wonder why Section 179 still exists. Three reasons.

First, Section 179 is selective. You elect which assets to expense and how much of each asset's cost to deduct. You can take 100% of one asset, 40% of another, and leave a third out entirely. Bonus depreciation, by contrast, is all-or-nothing per asset class.

Second, Section 179 covers a few categories bonus does not. Most notably, certain non-residential real property improvements like roofs, HVAC, fire protection, alarm systems, and security systems on commercial buildings can be expensed under Section 179 but generally aren't bonus-eligible (because they aren't 15-year QIP).

Third, the 2026 limits are generous:

• Maximum deduction: $2,560,000.
• Phase-out threshold: deductions reduce dollar-for-dollar once total qualifying property placed in service exceeds $4,090,000.
• Complete phase-out: at $6,650,000 of qualifying property.
• SUV sub-limit: deduction on a sport utility vehicle (6,001–14,000 lbs GVWR) is capped at $32,000, with the remainder eligible for bonus depreciation.

The catch: Section 179 cannot exceed your taxable business income for the year. It cannot create or increase a net operating loss. Bonus depreciation can. That distinction drives most of the decision-making below.

The Decision Framework: When to Use Which (or Both)

Most businesses use them together. The order matters.

Step 1: Section 179 first, on priority assets

Apply Section 179 to:

• Property that qualifies for 179 but not bonus. Roofs, HVAC, security systems, and similar non-residential real property improvements get expensed under 179 because bonus depreciation doesn't reach them.
• State conformity advantages. Many states fully conform to Section 179 but decouple from federal bonus depreciation (so a federal bonus deduction may require an addback on the state return, while a 179 deduction flows through cleanly). Check your state — this can be worth thousands.

Step 2: Bonus depreciation on everything else

After Section 179 is allocated, bonus depreciation automatically picks up the remaining basis on qualifying property — including any portion of an asset you only partially expensed under 179.

Step 3: Consider electing out of bonus when it hurts you

Bonus depreciation is great if the deduction is worth more this year than spread out. But electing out can be smarter when:

• You're in a low-bracket year and expect higher rates ahead. A new business with a $40,000 first-year profit doesn't get much value from a $300,000 deduction that creates a giant NOL. The carryforward is real, but its present value drops the longer it sits.
• You'll be selling assets soon. Bonus depreciation accelerates depreciation recapture, which is taxed as ordinary income on sale. If you'll sell the equipment in 18 months, the upfront deduction can flip into a recapture surprise.
• You're managing AGI for credits or deductions tied to thresholds. The QBI deduction, ACA subsidies, and other provisions phase out at specific income levels. A massive bonus deduction can overshoot the target.
• Your state decouples. A federal-only deduction without state benefit means tracking two depreciation schedules forever.

The election-out is made by asset class on a timely-filed return.

Step 4: For passenger vehicles, work the luxury auto caps

Passenger autos and light SUVs under 6,000 lbs GVWR are subject to "luxury auto" first-year depreciation caps — even with bonus depreciation. The result is that you cannot fully expense a $90,000 luxury sedan in year one, regardless of how generous the bonus rules look on paper.

Heavy SUVs (6,001 lbs GVWR and up) are different. Section 179 caps them at $32,000 in 2026, but the remaining basis is eligible for 100% bonus depreciation, which means the whole vehicle can typically be expensed in year one. The classic example: a $90,000 heavy SUV → $32,000 via 179 + $58,000 via bonus depreciation = $90,000 first-year deduction (subject to business-use percentage).

A Worked Example: $1.2 Million in 2026 Equipment

A specialty manufacturer placed the following in service during 2026:

Taxable income before depreciation: $950,000. The owner wants the largest possible first-year deduction without creating problems.

Section 179 allocation (apply to the assets that won't otherwise get bonus):

• HVAC: $185,000
• Shop roof: $310,000
• Heavy SUV: $32,000 (statutory cap)

Section 179 subtotal: $527,000 — well under the $2,560,000 cap, and within the $950,000 income limit.

Bonus depreciation on the remainder:

• CNC machine: $480,000
• Forklift: $42,000
• Computers: $58,000
• Heavy SUV remaining basis: $46,000
• Plant tooling: $74,000

Bonus subtotal: $700,000 — fully deductible regardless of income.

Total first-year deduction: $1,227,000. The owner has zero remaining basis on the depreciation schedule. Taxable income drops to negative $277,000, creating an NOL that can offset 80% of taxable income in future years.

Could they have done all $1.2M under Section 179? No — the $950,000 taxable income limit would have capped the 179 deduction. Could they have done it all under bonus depreciation? No — the HVAC and roof aren't bonus-eligible. Combining the two provisions is what unlocks the full write-off.

The Traps That Disqualify Property

The mechanics are generous, but a handful of details quietly take property out of bonus depreciation eligibility:

• Acquired by a related party. If you bought it from a sibling business, a controlled corporation, or another related party, the "first use" rules can knock out bonus eligibility.
• Floor plan financing. Auto dealers and some equipment dealers with floor plan financing interest deductions need to coordinate carefully; bonus depreciation is restricted in some cases.
• Real property trade or business electing out of the interest limitation. Businesses that elect out of the Section 163(j) interest expense limitation as a real property trade or business must use ADS — disqualifying that property from bonus.
• Predominantly personal use. A vehicle used 49% for business doesn't qualify for bonus depreciation in any portion. The threshold is 50% business use; below that, you're stuck with straight-line depreciation under ADS.
• Listed property recapture risk. If business use drops below 50% in a later year, you can face recapture of prior bonus depreciation.
• Placed-in-service timing. Property must be both ready and available for use and in the taxpayer's business by year-end. Delivery isn't enough — equipment sitting in a crate waiting for installation generally has not been placed in service.

Documentation Matters More Than You Think

Bonus depreciation and Section 179 are first-year deductions, but the IRS can question them years later — especially when there's an NOL carryforward or a major loss. To survive an audit, keep:

• Purchase invoices showing the asset, vendor, and date.
• Proof of payment and (for financed equipment) the loan or lease documents.
• Delivery and installation records to substantiate the placed-in-service date.
• Business-use logs for vehicles and other listed property — contemporaneous records are far more credible than reconstructed ones.
• Section 179 election on the timely-filed return (Form 4562, Part I).
• Election-out statements if you opt out of bonus depreciation for any asset class.

Cash Flow Planning: Don't Let the Tax Tail Wag the Dog

The biggest mistake small business owners make with bonus depreciation isn't a technical error — it's buying equipment they don't need because their accountant told them they could write it off. A $200,000 deduction is worth maybe $40,000–$74,000 in tax savings depending on your rate. You still spent the other $126,000–$160,000.

Buy equipment because the business needs it. Time the purchase to optimize the tax benefit if you can. Don't reverse the logic.

That said, when you do need the equipment, timing matters:

• December purchases work, but the property must be placed in service — not just paid for — before year-end.
• Used equipment qualifies, which means a strategic late-year purchase of a used asset can produce the same deduction as a new one at potentially lower cost.
• Financed purchases qualify too. You can deduct the full cost of equipment even if you financed 100% of it. (This is the source of many "deduct it all and finance it!" pitches at year-end equipment dealers. The deduction is real; the cash flow math depends on the loan terms.)

What This Means for Your 2026 Tax Planning

Three concrete actions to take before December 31:

1. Audit your fixed-asset list. Anything placed in service after January 19, 2025 should already be on a depreciation schedule reflecting 100% bonus or Section 179 treatment. If your 2025 return used the old 40% phase-down rate on post-January-19 property, you may have a Form 3115 accounting method change in your future.

2. Coordinate state and federal. Run two depreciation models if your state decouples from bonus. The federal-only benefit may not be worth the state tracking burden for marginal purchases.

3. Talk to your accountant before you sign large purchase orders in Q4. The interaction between Section 179, bonus depreciation, the QBI deduction, payroll tax planning, and (for pass-through owners) personal estimated taxes can flip the optimal answer.

Keep Your Books Audit-Ready

Aggressive first-year deductions only survive scrutiny when the underlying books support them. The depreciation schedule, fixed-asset register, purchase documentation, and business-use logs all need to tell the same story years after the deduction. That's hard to do with spreadsheets and a shoebox of receipts.

Beancount.io gives small businesses plain-text accounting that's transparent, version-controlled, and AI-ready — every transaction, every asset, every adjustment is human-readable and timestamped. When the IRS or your accountant asks how you arrived at the numbers on your 4562, you'll have a clean answer instead of a forensics project. Get started for free and see why developers, finance professionals, and small business owners are switching to plain-text accounting.