Personal Name vs. Business Entity: How to Sign Sponsorship Contracts the Right Way
You'll be referenced in a sponsorship contract in two main places.
The first will usually be in the opening paragraph where it says something like, "This contract is entered into by and between the Agency on behalf of its client, the Brand, and [Your name]."
If you have a legal structure for your business (e.g., LLC or S Corporation in the U.S.), then that needs to be listed under "[Your name]."
Instead of signing the contract as Justin Moore, you'll use your business entity for the services of (f/s/o) Justin Moore.

Note: if you haven't formalized your business legally yet or are wondering whether you need one, contact a local lawyer and/or tax advisor.
The second place you'll be referenced in a sponsorship contract is where you sign your name at the very end.
You must ensure that the "party" or "entity" they're referencing in this signatory area matches the opening paragraph.
While this might seem unnecessary or overly formal, there are two reasons you should care.
When the brand or agency is ready to write a check to you for the sponsorship, their finance team will usually ask for your tax form. All your paperwork must match for them to issue the payment.
In the unlikely event you ever get sued by someone in your audience who used the shampoo you recommended and their hair fell out, they can't come after your personal assets.

Get the ongoing support you need to set win-win pricing, submit spellbinding proposals, and negotiate like a pro.