There are certain limitations to the Section 179 deduction.
The two primary constrictions are that the asset(s) must be placed in service during the current tax year and the dollar limit on the deduction is capped at the total taxable income from all trades and businesses during the tax year.
See https://www.irs.gov/newsroom/new-rules-and-limitations-for-depreciation-and-expensing-under-the-tax-...
See also https://www.irs.gov/publications/p946#en_US_2019_publink1000299340
