It depends. This answer by TurboTax Pro PatriciaV gives excellent instruction on how to claim your start-up costs and how much in TurboTax: https://ttlc.intuit.com/replies/5146525
From the date your business is up and running, your monthly fee is no longer a startup cost and can be deducted under Commissions (actually Commissions and Fees is the category name). Your start-up expenses are the amount you spent prior to starting generating income.