if the business has started usually looked at as actively seeking customers, (examples include advertising your business or if you have a physical location a sign in the door - open for business), then the start-up costs are deductible/amortizable beginning with the date the business became active. no income is required. you can elect under reg 1.195-1(b) to capitalize start-up expenses but then they become non-deductible in future years
https://www.law.cornell.edu/uscode/text/26/195
reg 1.195-1(b) in part
A taxpayer may choose to forgo the deemed election by affirmatively electing (there has to be a statement to this effect included with the return) to capitalize its start-up expenditures on a timely filed Federal income tax return (including extensions) for the taxable year in which the active trade or business to which the expenditures relate begins. The election either to amortize start-up expenditures under section 195(b) or to capitalize start-up expenditures is irrevocable and applies to all start-up expenditures that are related to the active trade or business.
if you elect to capitalize - no future amortization is allowed. basically, you're stuck with the capitalized amount until the business terminates.
https://www.law.cornell.edu/cfr/text/26/1.195-1
