What does pay only when you file mean? Is it actually free to use TurboTax?

it's free to srart but only the following is included, and state is extra 

Situations covered (assuming no added tax complexity):

• W-2 income
• Interest or dividends (1099-INT/1099-DIV) that don’t require filing a Schedule B
• IRS standard deduction
• Earned Income Tax Credit (EITC)
• Child Tax Credit (CTC)
• Student loan interest deduction

Situations not covered: this is where the fees start

• Itemized deductions claimed on Schedule A
• Unemployment income reported on a 1099-G
• Business or 1099-NEC income
• Stock sales (including crypto investments)
• Rental property income
• Credits, deductions and income reported on other forms or schedules

 

 

 

the iRS has a free file site you may want to check them out

https://www.irs.gov/filing/free-file-do-your-federal-taxes-for-free 

Only TurboTax Free Edition is free. Free Edition is only for very simple tax returns that do not require any other forms or schedules besides Form 1040. Mike9241 listed what is and is not included in Free Edition. For any other edition you have to pay. You can prepare the tax return in TurboTax Online before you pay, but in order to print or e-file your tax return you have to pay the TurboTax fees. That's what it means when it says you have to pay when you file.