The simplified method for home business expenses allows you to take a standard amount per square foot of your home used for business, rather than requiring you to track each expense. The current rate is $5 per square foot and can't exceed 300 square feet.
If you choose to use the simplified method, you won't be able to use your home business expenses like mortgage interest and real estate taxes to reduce your business income, but you may still be able to include some as itemized deductions.
You can view a comparison of the simplified method and the regular method
here