Your tax return will include a Schedule C. You report all your business income and expenses from your own reliable records, regardless of any forms you get from clients.
If you accept electronic payments, you might receive a 1099-K from the payment processor(s). If you have a client that is another business and they paid you more than $600, they are supposed to send you a 1099-NEC. But you are expected to report all your income from your own records, even if you don't get 1099 forms. You would never issue a 1099 for payments you receive.
If your business makes payments of more than $600 to another person or business (subcontractor, some vendors) you may be required to issue a 1099-NEC for payments you made.
