Construction

A storage unit for your business is required to be reasonable and necessary expense for your business to be written of as a rent expense deduction.

If you have a separate shed on your property used "exclusively & regularly" for your business, you can take a business deduction for it.

Please remember to maintain accurate records of the storage costs & items that are within the shed, such as receipts.

If your shed is a regarded as a permanent attachment to your home, then it will be considered an improvement to your home subject to depreciation.

A  structure in considered permanent if it is an external attachment to your home and it is UNMOVABLE. Some examples include garages, barns, and sheds that are CEMENTED to where it stands.

You would make a deduction for your shed in the backyard the same way you would if you were utilizing a room in your home as Home Office Space.  Here are the steps:

1. Determine the square footage of the shed - Length x Width of the space
2. Compare this space to the square footage of the entire house LOT.  Since the shed is on the land portion of the home, you will need to use the entire lot square footage, not just the home.
3. The ratio (percentage) of Shed SF to Lot SF will determine the % of expenses you may deduct for shed costs.
4. Home lot costs for Shed Use can only relate to things Directly or Indirectly used by the shed location. In other words, if the shed does not have HVAC, Electric or Water/Sewer hook up, you may not deduct these costs as a percentage of the shed.  
5. You can deduct a percentage of the Mortgage/Lease payment, Property Taxes, City Improvement Taxes, Insurance, etc., that relate to the Home LOT.
6. Report these costs on Form 8829  https://www.irs.gov/forms-pubs/about-form-8829
7. You will also be able to take depreciation, if the company earns income.

For full disclosure of the HOW TO you may read in IRS.gov 

https://www.irs.gov/newsroom/how-small-business-owners-can-deduct-their-home-office-from-their-taxes