You should read the reference materials so that you can see what applies in a specific tax year, because things change, or get released as draft and then get finalized. Here are some of the links, when you do that search I suggested:

https://www.irs.gov/newsroom/irs-finalizes-regulations-for-100-percent-bonus-depreciation

https://www.carprousa.com/blog/self-employed-and-business-owners-2021-tax-code-179-and-bonus-depreci...

https://www.irs.gov/newsroom/additional-first-year-depreciation-deduction-bonus-faq

Always look at the dates, to know if it is Current.