An easier return would be something like this:
Interest and dividend income
Sales of a few stocks or mutual funds
Child care cost
A more complex return would be something like this:
Funding his defined contribution pension plan calculation
Several rental buildings as taxpayer is a real estate professional
Determination of rental losses as passive or active
Interest and dividends
Sales of stocks, bonds, options
Passive loss carryovers
Income from a trust that includes interest, dividends and rental income
Determination of advantage of election to expense property under Section 179
And a few other matters that I likely haven't thought of.
That's why a tax software is needed at CPA firms. My daughters return is very simple and I filed their State return directly on the Pennsylvania web site. No cost for that. The software wanted another $40 to file a State return. That's not gonna happen.