You may not need to buy anything new to get a big 2025 write-off. By converting a personal vehicle to qualified business use, OBBBA allows up to 100% bonus depreciation of the allowable basis—especially powerful for heavy SUVs and trucks. This guide explains the lower-of-cost-or-FMV basis rule, luxury-auto caps, why Section 179 doesn’t apply, and the documentation you need (mileage logs, FMV support, conversion date) to capture the deduction cleanly.