It depends on the type of work it was. The IRS requests a code to let them know the type of work and they will look at expenses to see if they correspond. Professional services are varied. If you fit into one of the groups below, you could have continuing education, computer and peripheral equipment, website and internet. Think about what you have to expend money on in order to produce the income. Look at your credit card bills.
https://www.irs.gov/pub/irs-pdf/i1040sc.pdf
541100 Legal services
541211 Offices of certified public accountants
541214 Payroll services
541213Tax preparation services
541219Other accounting services
