If the A/C system was installed in 2021, then no, you cannot claim the credit on your 2023 tax return. You must submit an amended 2021 return.
How do I amend my federal tax return for a prior year? (intuit.com)
For purposes of the energy credit for existing homes, costs are recognized in the year installation is completed.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
