Get your taxes done using TurboTax

Read the screen.  
It says you will be charged $39.99 if you chose to have the TurboTax account fees deducted from the federal tax refund.  

If you want to pay for this optional service plus the $19.99 then click on Pay with federal refund.  

If you only want to pay for the $19.99 Plus edition then click on Pay with credit card