If you are actively engaged in the business as of 12/31/21, then you file a schedule C and list your expenses and income. You can deduct up to $5000 of startup costs, if your startup costs are more than $5000 then you can deduct some now and some over time, there's a formula. If you lost money in your business, you can usually deduct that against your other income. This all goes on schedule C, and you will need to use the Turbotax Self Employed version (online) or the Home & Business version (if you buy the CD or download to install on your own computer). You don't have to make a profit to claim your expenses, or even get your first check, but you must be actively engaged in the business.
If you are only preparing for the business, and were not actively engaged in the business by the last day of 2021, you can't deduct your startup costs now, and you don't even file a schedule C with your 2021 return. However, whenever you do start actively performing the business activities (I guess in 2022?) you would file a schedule C and can include your previously paid-for startup costs, even though you paid them in a previous tax year.
