June 7, 2019 3:34 PM
You will get a letter from the IRS. They will assume your contribution was not qualified and will assess tax and a late fee for not paying it before. Then you would either have to pay or file an amended return to prove the contribution was qualified. The letter is pretty much automatic so I doubt there is a human who will look at it and decide not to bother.
*Answers are correct to the best of my ability at the time of posting but do not constitute legal or tax advice.*