Here is a good article. Scroll down for "When does a business begin.:
https://www.mileiq.com/blog/business-startup-costs-deduction/
So, just when does a new business begin? The courts have held that a new business begins for tax purposes when it starts to function as a going concern. It also must start performing the activities for which it was organized. (Richmond Television Corp. v. U.S., 345 F.2d 901 (4th Cir. 1965).)
The IRS says that a venture becomes a going concern when it acquires all the assets necessary to perform its intended functions. It must also put those assets to work. Your business begins when you start doing business, whether you are actually earning money.
For example, if your business involves providing a service to customers or clients. This includes accounting, consulting, financial planning, or law services. Your business begins when you first offer your services to the public. No one has to hire you; you just have to be available for hire. For example, a consultant’s business begins when he or she is available for hire by clients.
