The key test is regular and exclusive use: a specific area of your home used only for business. A spare room used as your office qualifies; the kitchen table you also eat at does not. The space must also be your principal place of business or where you regularly meet clients.
The simplified method deducts a flat $5 per square foot up to 300 square feet, so a maximum of $1,500, with no receipts needed. The regular method deducts the business-use percentage (office square footage divided by total home square footage) of your actual home costs, which can be larger but needs records.
This deduction is for the self-employed. Employees who work from home generally cannot deduct a home office on their federal return under current rules.

