In fact, filing an amended 2022 tax return, after the initial filing, is easy to do (I have done it before on prior years). But, agreeing with improvius, the issue will be whether the IRS interprets the reservation and the associated contract to be a "written binding contract."The grandfathered tax credit provision would apply if you take delivery any time in the rest of 2022 or 2023. You would probably have to re-file your 2022 taxes if you take delivery after submitting them. This is all assuming the "contract" meets IRS requirements.