Deductions & credits

It is great news.  I am filing a 8917 for 2019.  How do I file one for 2018 if I do not amend my return?  Maybe I am misunderstanding, but each year is limited in deduction based on income.  So based on my understanding I would need to file a form 8917 for 2018 which would reduce my taxable income (AGI) resulting in a need to amend the 2018 return?

 

Thank you.