Download and view or print the PDF of your return and look for form 2210. Turbotax might not have prompted you to calculate a penalty if it did not detect an obvious penalty situation. (There is also a step where you are asked "Do you want to check to see if you need to include a penalty" but you might have gone past that step without noticing it.)
Unless you owe a huge penalty, the only thing that might happen as a result of not including the form is a bit more interest owed.
