I'm new to Secret Shopping and wanted to find out how everyone reports income when they file their taxes. Do you report all of the money you earned and then the expenses as well?

i.e. I go to a restaurant and it's required I order $15 worth of food and then get paid $18 as a reimbursement.

Should I file $18 as income and then the $15 as a business expense?

Thanks in advance for the advice!