OBBBA reopened a first-year deduction window that many owners have been waiting for: 100 percent bonus depreciation is back for eligible assets acquired and placed in service after January 19, 2025.

At the same time, Section 179 expensing limits increased sharply, which means many businesses now have two large first-year write-off tools available for the same purchase.

The exposure assumes these two tools are interchangeable.

They are not.

This is not a “which gives the biggest deduction” question. It is a loss mechanics and future tax usefulness question, with three common failure points:

You create a loss that turns into an NOL, which does not help with self-employment tax later.
You choose Section 179 and the business income limitation blocks the deduction, leaving you with taxable income now and a carryover later.
You trip the excess business loss rules, and your “big first year deduction” becomes delayed and treated like an NOL anyway.

This briefing is a decision screen for owners buying equipment, vehicles, software, and qualified improvement property.

What changed after OBBBA

1) 100 percent bonus depreciation is back

OBBBA restored 100 percent first-year bonus depreciation for eligible assets acquired and placed in service after January 19, 2025.

Eligible assets include most depreciable personal property, such as equipment, computer hardware, certain vehicles, and commercially available software. Bonus depreciation can also apply to qualified improvement property, which is interior improvements to nonresidential buildings with important exclusions.

There is also an election option: for property eligible for first-year bonus depreciation placed in service in the first taxable year ending after January 19, 2025, you can elect 40 percent instead of 100 percent, then depreciate the remaining cost under regular rules. This can matter if you expect higher rates after 2025.

2) Section 179 limits increased

For assets placed in service in tax years beginning in 2025, OBBBA increased the maximum Section 179 deduction to $2.5 million with a phaseout beginning when total Section 179 eligible assets placed in service exceed $4 million.

For tax years beginning in 2026, the maximum increases to $2.56 million, and the phaseout threshold increases to $4.09 million.

Section 179 can apply to many types of equipment and software, and it can also apply to qualified improvement property and certain building components like roofs, HVAC, fire protection and alarm systems, and security systems in specific nonresidential contexts.

There is also a special Section 179 limit for heavy SUVs in the 6,001 to 14,000 GVWR range, while bonus depreciation has no comparable cap for that vehicle category if otherwise eligible.

The difference that matters: Section 179 has limits, bonus does not

Bonus depreciation is mechanically simpler:

no annual cap
no phaseout threshold
no business income limitation

Section 179 is generous, but it is gated by restrictions that can block or delay the deduction.

The business income limitation is the main trap

Section 179 cannot create an overall business loss. The allowable deduction is limited to the taxpayer’s aggregate taxable income from the active conduct of a trade or business. Disallowed amounts carry forward until usable.

This shows up in real life when an owner purchases a large amount of equipment in a year when business income is lower than usual. The deduction you thought you were taking now becomes a carryover.

Bonus depreciation does not have this limitation. It can create a loss.

The self-employment tax and NOL angle most owners miss

If bonus depreciation creates a negative taxable income result, it often produces a net operating loss. NOLs can carry forward indefinitely, but generally cannot shelter more than 80 percent of taxable income in the carryover year.

The key planning consequence in the source is this: NOL deductions in carryover years typically do not reduce self-employment income, so the future year benefit may be weaker than owners expect from an “all-in” first-year deduction.

Section 179 carryovers can be different: when a carried-over Section 179 deduction is eventually used, it reduces taxable income and can reduce self-employment income.

This is why the choice is not just timing. It is about which form of loss is created and whether it will be useful later.

The excess business loss rule is a second gate

Even if bonus depreciation technically creates a large business loss, individual taxpayers can run into the excess business loss rule.

The source provides thresholds for 2025 and then notes reduced thresholds for 2026 under OBBBA, with excess losses treated as an NOL carryover. That treatment delays benefit and preserves the same NOL limitation issues discussed above.

Planning implication: a large bonus depreciation deduction can still become partially delayed and converted into NOL form by this rule.

Decision screen: when to lean bonus and when Section 179 can matter

Default posture in many cases

The source states the usual recommendation is to claim 100 percent bonus depreciation to the extent allowed rather than using Section 179 for the same assets, because bonus depreciation avoids the Section 179 limitations.

When Section 179 can be strategically useful

Section 179 can be useful when:

You expect higher business income later and want a carryover that can reduce future taxable income and self-employment income
Bonus depreciation would create an NOL that you cannot use efficiently due to the 80 percent limitation, or because it will not help with self-employment tax in the years you use it
You are managing around the excess business loss thresholds and do not want your loss converted into NOL form

Year planning note

The source highlights an election to take 40 percent bonus depreciation in certain 2025 timing scenarios to manage rate expectations. This is a planning lever if you believe post 2025 rates are higher and you do not want to burn deductions at lower rates.

What to do next

If you are placing significant assets in service, your first-year depreciation choice should be modeled with:

Projected business income, not just current year income
Whether you are near excess business loss thresholds
Whether the self-employment tax reduction in future years is a priority,
Whether you need deductions now, or prefer carryover usefulness later

We can review your planned asset purchases and run a conservative decision model that pressure-tests bonus depreciation vs. Section 179 through the loss-rule gates before you lock in your filing posture. Contact us today.

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Disclosure: This article is for educational purposes only and is not tax or legal advice. Tax outcomes depend on your facts, entity type, and documentation.