If you do not want to take the Retirement Savings Contribution Credit, you will have to tell TurboTax that you were a full-time student in 2018. If you have 401K contributions on your W-2 or any IRA contributions, TurboTax knows you qualify for the credit which is reported on Schedule 3 and requires an upgrade to Deluxe.
To get around this, you can tell TurboTax that you were a student. Being a student will disqualify you for the credit and TurboTax will not force you to upgrade. But you won't get the credit either. To do this:
Go back to the Retirement Savings Contribution Credit interview and answer YES to 'Did you make contributions in 2018?' and 'Were you a full-time student?' questions. You do not qualify for the credit if you were a full-time student in 2018. And if you don't qualify, TurboTax will remove the credit. To get back there, go to Deductions & Credits or type ''saver's credit'' into the search bar, and use the Jump To link.
If you want the credit without upgrading, you can look into the Free File Program. If you qualify, you can file your tax return through them for free and get the credit. Keep in mind however that you cannot use your regular TurboTax account even though it says 'TurboTax' on the qualifier screen. This program goes through the IRS and is not tied to your TurboTax account. Free File Program - Requires a Separate Account