Can you deduct ChatGPT API costs for a side project?

Generally, yes — ChatGPT API costs can be deductible, but only if they’re part of a real business activity with a profit motive.

Here’s the practical breakdown under U.S. federal tax rules:

If your side project is a business

If you’re operating it as a business, you can usually deduct ordinary and necessary expenses, and API usage fees may qualify if they’re directly tied to building or running the project. These are commonly reported on Schedule C for a sole proprietorship.

If the project is still pre-launch

If you’re building the product before it officially starts operating, some costs may be treated as startup expenses under IRS rules rather than immediately deducted as regular business expenses.

• You may be able to deduct up to $5,000 of startup costs in the first year the business begins, but that deduction is reduced if total startup costs are high.
• Any remaining startup costs are generally amortized over 15 years.

If it’s just a hobby

If the project is mainly for fun, personal learning, or experimentation without a real profit motive, it’s usually treated as a hobby, and hobby expenses generally are not deductible on your federal return.

What you should verify

• Whether your project really qualifies as a business vs. hobby
• Whether the API costs are startup costs or current business expenses
• Whether you have good records showing business use
• Whether your state tax rules differ

For anything material, it’s worth checking with a CPA or tax professional, because the exact treatment depends on your facts.