Garage space used for home office

So we would need to look at Publication 587 for the answer.  Under Separate Structure we find:

You can deduct expenses for a separate free-standing structure, such as a studio, workshop, garage, or barn, if you use it exclusively and regularly for your business. The structure does not have to be your principal place of business or a place where you meet patients, clients, or customers.

So assuming you meet the test of exclusively and regularly for your business you could deduct this as a business expense.  

If this is a home office for you as an employee, employees may only take the home office deduction if they maintain the home office for the convenience of their employer. An employee's home office is deemed to be for an employer's convenience only if it is: a condition of employment, necessary for the employer's business to properly function, or needed to allow the employee to properly perform his or her duties. Currently employee business expenses are not allowed unless the  individuals is employed as Armed Forces reservists, qualified performing artists, fee-based state and local government officials, and employees with impairment-related work expenses.

Thank you for the opportunity to answer your questions @SarahMac7 

All the best,

Marc T.

TurboTax Live Tax Expert

Yes, you can
IF

you are self-employed

AND

the area in the garage is used EXCLUSIVELY and it must be your principal place of business.

Suppose someone sells Doodads. They keep their Doodad supply in the garage in the corner and the area is 4'x4'. Nothing else is ever kept there, this is where all the Doodads are stored until they're sold and would qualify as a home office.

Suppose you are a florist. You do your work in the garage after you pull the cars out. This doesn't qualify for a home office since you do other things in addition to floral work there.

Here's some guidance:

IRS How small business owners can deduct their home office from their taxes

This is an attached garage with desk space and storage ONLY used for business. thank you.