Section 179 vs. 100% Bonus Depreciation Under OBBBA: How Small Businesses Should Choose Their Equipment Write-Off Strategy in 2026

Imagine you just bought a $400,000 CNC machine for your shop in March. Your accountant says you can deduct the entire cost this year. Then she pauses and asks one more question: "Do you want to use Section 179, bonus depreciation, or a mix of both?" You blink. You thought there was only one way to expense equipment. You thought wrong.

The One Big Beautiful Bill Act (OBBBA), enacted in 2025, reshaped both of the major first-year write-off tools for tangible business property. Section 179 limits jumped sharply — the cap is $2.56 million for tax years beginning in 2026, with a phase-out threshold of $4.09 million, both indexed annually for inflation. Bonus depreciation, which was scheduled to phase out at 40% in 2025, was restored to a permanent 100% for property acquired and placed in service after January 19, 2025.

That sounds like a generous problem to have. But the two provisions are not interchangeable, and choosing the wrong one — or applying them in the wrong order — can leave deductions stranded, distort your state tax bill, or create losses you cannot use. Here is how to think about the choice.

The Two Tools, Side by Side

Both Section 179 and bonus depreciation let you write off the cost of qualifying property in the year you place it in service, instead of spreading the deduction over five, seven, or fifteen years through MACRS depreciation. After that, they diverge.

Section 179: targeted, capped, taxable-income-limited

Section 179 is an election — you choose, asset by asset, how much of the cost to expense. The rules that matter most:

• 2026 cap: $2,560,000 of qualifying property per year.
• Phase-out: the cap drops dollar-for-dollar once total qualifying purchases exceed $4,090,000, and the deduction zeroes out at roughly $6.65 million.
• Taxable income limit: Section 179 cannot create or deepen a loss. If your business's taxable income is $200,000, your Section 179 deduction is capped at $200,000 even if you bought $1 million of equipment.
• Carryforward: any disallowed Section 179 carries forward indefinitely, still subject to the taxable income test each future year.
• Real property bonus: Section 179 can be used on certain non-residential improvements that bonus depreciation cannot touch — roofs, HVAC systems, fire protection, alarm and security systems on buildings already in service.
• Vehicle caps: SUVs over 6,000 pounds gross vehicle weight rating are capped at $31,300 of Section 179 in 2026; light passenger vehicles top out around $12,200 in first-year depreciation.

Bonus depreciation: automatic, uncapped, loss-friendly

Bonus depreciation is the default for qualifying property unless you elect out. The differences from Section 179 matter:

• Rate: 100% for property acquired and placed in service after January 19, 2025, with no sunset under OBBBA.
• No dollar cap. A manufacturer that buys $20 million of equipment can write off the entire $20 million.
• No taxable income limit. Bonus depreciation can create or enlarge a net operating loss (NOL), which carries forward to offset up to 80% of taxable income in future years.
• Used property eligible. As long as the asset is new to you, bonus depreciation applies — important for buyers of pre-owned equipment, fleets, and acquired businesses.
• Class-by-class election out. You cannot pick and choose individual assets; if you elect out of bonus, you elect out for an entire class (5-year, 7-year, etc.) for that tax year.
• Real property generally excluded (with a narrow new exception under Section 168(n) for qualified production property — manufacturing, agriculture, chemical production — placed in service before January 1, 2031).

The Order of Operations the IRS Imposes

This is the part that catches owners off guard. When you place property in service, the IRS applies the deductions in a specific sequence:

1. Section 179 is taken first, up to your election and within the cap.
2. Bonus depreciation applies next, against the remaining basis.
3. MACRS depreciation handles whatever is left.

So if you buy a $50,000 piece of equipment and elect $20,000 of Section 179, bonus depreciation is computed on the remaining $30,000. At a 100% bonus rate, the rest is fully deducted in year one regardless. At a 60% bonus rate (which still applies to certain transition property and to taxpayers who elect the prior-year rate), $18,000 of the remaining $30,000 is bonus, and $12,000 is depreciated under MACRS.

This sequencing is mechanical, but it has real consequences. If you front-load too much Section 179 in a low-income year, you waste deductions to a carryforward you may not need. If you skip Section 179 entirely on assets that bonus depreciation cannot reach (like a new HVAC unit on an existing office building), you forfeit a write-off available nowhere else.

When Section 179 Is the Right Choice

Despite bonus depreciation being the bigger, simpler hammer, Section 179 still wins in several common situations.

You bought property that bonus depreciation does not cover

This is the single most important Section 179 use case. Bonus depreciation requires property with a recovery period of 20 years or less, which excludes most real-property improvements to buildings already placed in service. Section 179, by statute, covers:

• Roofs, including replacements and overlays
• HVAC units and rooftop systems
• Fire protection, alarm, and security systems
• Qualified improvement property (interior, non-structural improvements to non-residential buildings)

If you replaced the roof on your warehouse for $180,000, bonus depreciation likely yields nothing. Section 179 yields a $180,000 deduction, subject to the cap and income limit.

You operate in a state that decouples from federal bonus

Roughly a third of states fully conform to federal bonus depreciation. The rest range from partial conformity (a fixed percentage, often 0%) to outright disallowance with required addbacks. New York, New Jersey, California, Pennsylvania, and several others either do not allow bonus depreciation at all or accept only a portion. Most of these same states allow Section 179, sometimes with their own lower caps.

If your business is a single-state operation in a non-conforming state, electing Section 179 instead of bonus depreciation often produces a closer match between your federal and state deductions, reducing the painful bookkeeping of separate state depreciation schedules that drag on for years.

You want surgical control over which assets get expensed

Bonus depreciation is all-or-nothing within an asset class. If you want to expense five of the seven 7-year-class assets you bought and depreciate the other two normally — to manage a Section 199A qualified business income deduction, an interest expense limitation under Section 163(j), or a state-level addback — Section 179 lets you make that choice asset by asset.

Your taxable income is comfortably above the deduction

Because Section 179 cannot create a loss, it works best when you have plenty of profit to absorb it. Profitable, equipment-heavy businesses — dental practices, contractors, machine shops, transportation companies — are the textbook Section 179 candidates.

When Bonus Depreciation Is the Right Choice

For larger purchases or businesses with uneven income, bonus depreciation is usually the more powerful tool.

You bought more than the Section 179 cap

The 2026 Section 179 cap is generous, but a single piece of heavy equipment can blow through it. A long-haul logistics company replacing a fleet, a factory installing a new production line, or a medical practice buying imaging equipment can hit the $2.56 million cap in one transaction. Bonus depreciation has no such ceiling.

You are in a low-income or loss year

The Section 179 taxable-income limit means a startup in its first investment-heavy year, a real estate operator with passive losses, or a business hit by a one-time slump cannot use Section 179 effectively. Bonus depreciation, in contrast, sails through the limit, creates an NOL, and parks the deduction for use against future income.

A common mistake here is electing Section 179 in a loss year and then carrying the disallowed amount forward — only to have it stay disallowed for years because each future year has its own income limit. Bonus depreciation, by creating an NOL instead, gives you a deduction with a different (and generally more useful) carryforward set of rules.

You bought used equipment from an unrelated party

Both provisions allow used property under current law, but bonus depreciation is the cleaner path. Many practitioners default to bonus depreciation for used equipment to avoid arguments about whether the property was really "new to the taxpayer."

You want to reduce administrative complexity

Bonus depreciation is automatic. Unless you affirmatively elect out, you get it. Section 179 requires an election, the calculation of an income limit, tracking carryforwards, and matching against vehicle and SUV caps. For businesses without a tax department, the simpler tool wins.

The Hybrid Move That Most Owners Miss

The smartest approach is rarely "Section 179 only" or "bonus only." It is a combination, sequenced deliberately.

A worked example: a contractor in 2026 with $1.8 million of taxable income before depreciation buys:

• A $250,000 CNC plasma cutter (7-year property)
• A $90,000 work truck rated over 6,000 pounds GVWR
• A $120,000 HVAC overhaul on the office building
• A $40,000 used pickup (light vehicle)

The contractor's accountant might:

1. Elect Section 179 on the $120,000 HVAC (because bonus does not apply to it).
2. Elect Section 179 on the truck up to the $31,300 SUV cap, then take 100% bonus on the remaining $58,700 of the truck.
3. Take 100% bonus on the $250,000 CNC.
4. Take the first-year passenger vehicle limit on the used pickup (around $12,200 first year for vehicles under 6,000 pounds GVWR), with the rest depreciated normally.

Total first-year deduction: roughly $471,200 of the $500,000 spent, with the deduction layered to respect taxable income, vehicle caps, and the building-improvement gap.

The Bookkeeping Implications

These choices live and die on clean records. Specifically, you need to be able to show, for every fixed asset:

• Date placed in service
• Cost basis (including freight, installation, and sales tax)
• Whether it is new or used
• GVWR for vehicles
• Recovery period and asset class
• Section 179 election made (or not)
• Bonus depreciation taken (or elected out)
• State adjustments where conformity differs

Most owners do not realize how many decisions they are making until they hit an audit, a partnership change, or a sale of the business. At that point, every asset's full lifecycle has to be reconstructed from invoices, bank statements, and depreciation schedules. If your records are scattered across spreadsheets, accounting software exports, and PDFs, the reconstruction can take weeks. If they are version-controlled in plain text — every transaction, every adjustment, every election captured in a readable, diffable format — it takes minutes.

That is also why pairing aggressive depreciation strategies with disciplined bookkeeping matters more than the headline deduction. A $2 million write-off you cannot defend is worth much less than a $1.5 million write-off you can.

Common Mistakes to Avoid

A few traps owners and even some preparers walk into:

• Forgetting the placed-in-service rule. A piece of equipment is not deductible the year you order or pay for it; it is deductible the year it is operational and ready for its intended use. December 30 deliveries that sit in a crate until January are 2027 deductions, not 2026.
• Treating bonus depreciation as a freebie. Yes, it is automatic, but it can crash your Section 199A QBI deduction in a year when you wanted to maximize it, blow a financing covenant tied to EBITDA, or strand state-level addbacks.
• Mixing Section 179 with mid-quarter convention awareness. Section 179 reduces the basis used in the mid-quarter calculation, sometimes pulling you into or out of the mid-quarter rule unexpectedly.
• Ignoring recapture. If business use of an asset drops below 50% within its recovery period, Section 179 (and listed-property bonus) gets recaptured as ordinary income. This is a recurring surprise for vehicle owners whose business mileage drops in later years.
• Taking 100% bonus in a year with a Section 163(j) interest limit. Larger expensing reduces taxable income, which reduces the adjusted taxable income base for the interest deduction limit, which can permanently strand interest expense.

A Quick Decision Framework

When a new asset hits your books, walk through this short checklist:

1. Is the property eligible for bonus depreciation? (20-year-or-less recovery period, tangible, not building structure.) If no, consider Section 179.
2. What is your projected taxable income? If low or negative, bonus depreciation is usually preferable to Section 179.
3. Does your state conform to federal bonus depreciation? If not, Section 179 may simplify your state position.
4. Are vehicle or building-improvement caps in play? Each requires its own treatment.
5. Do you have a strategic reason to spread the deduction — Section 199A optimization, interest limit, NOL planning, financing covenants? If so, consider electing out of bonus on a class and using Section 179 selectively.

For most small businesses with steady profits, ordinary equipment, and federal-conforming states, the answer in 2026 will be: take Section 179 on building improvements you cannot bonus, take 100% bonus on everything else, and move on. For everyone else, talk to a tax professional before the year closes — not after.

Keep Your Equipment Records Clean From Day One

Whether you choose Section 179, bonus depreciation, or a hybrid, the deduction is only as defensible as the records behind it. Beancount.io provides plain-text accounting that gives you complete transparency and version history over every transaction, asset, and adjustment — no black boxes, no proprietary formats, and no scrambling at year-end. Get started for free and see why developers and finance professionals are switching to plain-text accounting.