Section 179 vs. bonus depreciation
They're not competing options — they stack, in a fixed order, on the same asset. Here's exactly how, and why you'd still elect Section 179 when bonus depreciation is already 100%.
Two different tools, same goal
An election you make asset by asset, capped in total dollars and limited to business taxable income — a scalpel, letting you choose exactly which purchases to expense immediately.
Applies automatically to qualifying property (unless you elect out), has no dollar cap, and can create a business loss — a broader, less selective tool that currently expenses 100% of qualifying basis regardless of amount.
The 2026 numbers
The 100% bonus rate and its permanence come from the One Big Beautiful Bill Act (Public Law 119-21), applying to qualifying property acquired and placed in service after January 19, 2025 — a genuine reversal of the phase-down schedule that had been reducing bonus depreciation each year since 2023.
The stacking order
The income limit that only applies to one of them
Section 179 cannot reduce business taxable income below zero — it's capped at whatever the business actually earned that year, before the deduction itself. A business with $40,000 of profit buying a $100,000 machine can take at most $40,000 under Section 179 that year; the rest carries forward. Bonus depreciation has no such floor. The same $100,000 machine, run through bonus depreciation instead, can push that $40,000-profit business into a loss, which then carries forward under the net operating loss rules rather than the Section 179 carryforward rules — two different carryforward mechanisms with different limitations.
A full worked example
A landscaping business with $180,000 of profit before any equipment deduction buys a $70,000 heavy-duty truck (GVWR over 6,000 pounds, so it falls outside the passenger-vehicle depreciation caps) and $45,000 of other equipment in the same year — $115,000 in total qualifying purchases.
The truck is capped at $32,000 under Section 179's heavy-vehicle rule. The $45,000 of other equipment has no such cap and can be elected in full under Section 179. Total Section 179 election: $32,000 + $45,000 = $77,000 — well under both the $2,560,000 annual limit and the $180,000 income limit.
The remaining basis on the truck ($70,000 − $32,000 = $38,000) gets 100% bonus depreciation, adding another $38,000. Total first-year deduction across both assets: $77,000 (Section 179) + $38,000 (bonus depreciation) = $115,000 — the full cost of everything purchased, expensed entirely in year one, split across the two mechanisms because of the vehicle-specific Section 179 cap.
Why elect Section 179 at all
If bonus depreciation already expenses 100% automatically, Section 179's main practical value is selectivity: a business expecting a much higher-profit year next year, currently sitting near breakeven, might deliberately elect Section 179 on only some of this year's purchases (bounded by this year's income limit) and rely on bonus depreciation — or hold off on bonus depreciation via an election-out on specific asset classes — to shift more deduction into the future higher-income year. This kind of timing control isn't available with bonus depreciation alone, which applies broadly rather than asset by asset.
State conformity: the other reason
Many states don't fully conform to federal bonus depreciation rules — some disallow it entirely, others cap it well below 100%, while still allowing a limited state-level Section 179 deduction. A business filing in one of these states can face a real federal-versus-state depreciation gap even when the federal outcome (full first-year expensing) is identical regardless of which mechanism is used. Checking state conformity before assuming a federal deduction carries through to the state return is worth doing before, not after, the purchase.
Requiring the business to add back the bonus depreciation amount on the state return and depreciate the asset over its normal MACRS schedule for state purposes instead.
A state limit of $25,000, for instance, against a federal limit of $2,560,000, meaning the state and federal Section 179 deductions on the same asset can differ by orders of magnitude.
Run the full first-year deduction, including the Section 179 and bonus depreciation interaction above, through the Section 179 calculator.
Frequently asked questions
Section 179 is an election, capped at $2,560,000 for 2026 and limited to business taxable income, that lets you choose which qualifying assets to expense immediately, asset by asset. Bonus depreciation, currently 100% and permanent under the One Big Beautiful Bill Act, applies automatically to qualifying property unless you elect out, has no dollar cap, and can create or increase a net operating loss, which Section 179 cannot do.
Yes, and in a specific order: Section 179 is applied first, then bonus depreciation applies to whatever basis remains after the Section 179 election, then regular MACRS depreciation applies to anything still left. A $70,000 asset with a $32,000 Section 179 cap (a heavy SUV, for instance) can take $32,000 under Section 179 and 100% bonus depreciation on the remaining $38,000, fully expensing the asset in year one despite the Section 179 cap.
Selectivity and state conformity are the two real reasons. Section 179 lets you choose specific assets to expense rather than applying one rate to everything, useful when you want to preserve deductions for a future year with higher income. Many states also cap or disallow bonus depreciation while allowing a limited Section 179 deduction, so the federal-versus-state gap can matter even when the federal outcome is identical either way.
No — Section 179 is capped at the business's taxable income for the year (before the deduction itself), so it cannot push profit below zero. Bonus depreciation has no such limit and can create or deepen a net operating loss, which then carries forward to offset future income under the NOL carryforward rules.
Under current law, yes — the One Big Beautiful Bill Act made 100% bonus depreciation permanent for qualifying property acquired and placed in service after January 19, 2025, removing the phase-down schedule that had been reducing the rate each year since 2023. Property acquired before that date under a pre-existing binding contract still follows the old phase-down schedule, so the applicable rate depends on the acquisition date, not just the placed-in-service year.
Glossary:Section 179,Bonus Depreciation