My daughter started a farm based business when she turned 18 last fall. Do we claim her business income and expenses on our tax filing since she is a dependent?

[VolvoGirl]

You don't include their income on your return. It would only go on their return if they are required to file one.  To file a separate return for your dependent you need to set up a new account.  Online is only good for one return per account.  You can use the same email address for 5 accounts.  They can probably use the Free Edition.  How to start a new online return

Https://ttlc.intuit.com/questions/1894512-how-do-i-start-another-return-in-turbotax-online 

Or the Free File website.  In order to use the Free File program, you have to start it at a special website.  Click on the Orange button I Qualify, Let's get Started

https://freefile.intuit.com/

Be sure on their return they check the box that says they can be claimed on someone else’s return.

[Irene2805]

As VolvoGirl explained, your daughter's income does not go on your return, but your daughter's own return.  Since she is still your dependent, she will only have to file a return if her net income from self-employment was $400 or more.  [She will also have to file if her earned income (from a job) is $12,200 or more; or any unearned income (interest, dividends, etc) is $1,100 or more.]

If she does file a return, to indicate that she is a dependent of someone else, she should follow these steps:

1. Go into your return and click My Info tab in the black bar on the side of your screen.
2. Click  Edit next to your name.  
3. On the Your Personal Info screen, in section #3, for the question Someone else can claim me on their tax return, mark the Yes circle.  
4. Then mark the circle And this person will claim me on their 2019 return and click Continue.
5. Continue with the rest of the return.

IMPORTANT:  If you haven't yet filed your return, you should e-file before your daughter.  Once her SSN is entered into the IRS system on a return, you will not be able to e-file your return. and will have to print and mail yours in.