It was about 2017 when the IRS has began cracking down on schools that send out a 1098-T with box 1 blank. They were not always accepting an amount in box 2, of a 1098-T, as proof that you paid tuition. There was no additional proof required at the time you filed your return. The IRS wants the proof , now, after the fact. TurboTax did nothing wrong. There was nothing you could do to prevent this. This is a failure of the tax system. The school could have done a better job with the 1098-T, but even that statement is an oversimplification.
You only need to prove you actually paid tuition, with school statements and cancelled checks and/or bank or credit card statements. School billing statements, showing qualified expenses and your payments credited to the account is usually best.
