Section 179 lets you expense a qualifying business vehicle in the year it is placed in service instead of depreciating it over six years. But the real first-year number is decided by three limits — the "write off 100% of your truck" framing skips all three.
The three limits (2026 figures, verified against irs.gov):
- Business use must exceed 50%. At 50% or below you cannot elect Section 179 or bonus depreciation on a vehicle at all — you are limited to straight-line depreciation.
- The 6,000-lb GVWR line (GVWR is on the driver-door jamb sticker):
- Passenger auto under 6,000 lb — "listed property" capped by §280F. 2026 first-year cap: $20,300 with bonus depreciation / $12,300 without (Rev. Proc. 2026-15).
- Heavy SUV, 6,000–14,000 lb — separate §179 cap of $32,000 for 2026 (§179(b)(5)); the remaining basis is eligible for 100% bonus depreciation.
- Cargo van or pickup with a bed of at least 6 feet, over 6,000 lb — escapes the SUV cap entirely: full §179 (up to $2,560,000 for 2026) plus 100% bonus on the rest.
- You only ever deduct the business-use share. 80% business use on a $70,000 truck is a deduction built on a $56,000 basis, not $70,000.
100% bonus depreciation was reinstated by the One Big Beautiful Bill Act (P.L. 119-21) for qualified property placed in service after 19 January 2025 — which is why heavy SUVs and work vehicles can currently be close to a full first-year write-off of their business-use share.
Recapture: if business use later drops to 50% or less during the recovery period, §179(d)(10) recaptures the excess benefit as ordinary income. This is why business-use percentage needs a contemporaneous mileage log.
You cannot combine §179 with the standard mileage rate on the same vehicle — the standard rate already includes a depreciation component (Rev. Proc. 2010-51). It is one method or the other.
Estimate your own number with the Section 179 Vehicle Deduction Calculator. ExpenseBot captures the purchase invoice and running fuel/repair/insurance receipts from Gmail into a Google Sheet you own, so the actual-expense side of a vehicle deduction has a paper trail. Estimates — confirm with your tax professional.