2018 tax form 5329 was completed by Turbo Tax. I have never had this before and I have no idea why I have it now or where the number comes from.

[macuser_22]

There are possible several reasons.  If you are using the desktop version then switch to the forms mode and view the 5329 form  What line has the penalty on?

[DawnC0]

Probably because you have overcontributed to your IRA (or some other tax-favored account), or at least TurboTax thinks you have based on what you entered.  

It is that or you took an early withdrawal from a retirement account.  You can use Forms Mode to view the form and see which type of account is causing the problem.  If you have excess IRA contributions, you can remove them before 04/15 and remove the penalty.