You can deduct your start-up costs in the tax year your business begins (i.e., when you are open for business).
Up to $5,000 can be deducted with the balance amortized (subject to restrictions).
See https://www.irs.gov/publications/p535#en_US_2021_publink1000208919
See also https://www.irs.gov/newsroom/heres-how-businesses-can-deduct-startup-costs-from-their-federal-taxes
