There is no startup "credit". You can deduct startup costs. A credit is different from a deduction.
For 2021, your startup costs are either deducted, or amortized over 15 years. If your startup costs are less than $5000 you can deduct them all at once. If they are more than $5000 but less than $50,000, you can deduct $5000 in the first year but the rest must be amortized (spread out) over 15 years. If more than $50,000, a different formula applies.
For 2022 and 2023 you no longer have startup costs, you just have ongoing business expenses which are recorded in the usual way.
If your startup costs in 2021 were more than $5000, you must go back and file an amended 2021 tax return to list ALL your startup costs (not just $5000) and get your amortization schedule, that will tell you how much you deduct in each future year. Then for 2022, 2023 and so on, you will include the amortized startup costs as one of your business expenses along with your ongoing (routine) expenses.
