Hello, is a percentage of a storage unit deductible for business? If so, how do I enter that in TurboTax?

[JamesG1]

I believe that you could.  See this TurboTax Help under Principal place of business.

“If your home office is in a separate, unattached structure—a loft over a detached garage, for example—you don’t have to meet the principal-place-of-business or the deal-with-customers test. As long as you pass the exclusive- and regular-use tests, you can qualify for home business write-offs.”

To report these expenses,

• You would report that you use the office space exclusively and regularly for business.
• You would report that the office space is a separate structure.
• You would report the address of the office space.
• You would report that you rent the office space.
• You would report the percentage of the space devoted to the office space.