But that does not tell us anything. What authoritative cites did they refer to?
Section 25D(e)(8) (A) states : In general Except as provided in subparagraph (B), an expenditure with respect to an item shall be treated as made when the original installation of the item is completed.”
That is in contrast to section 48 for a commercial energy credit which specifically states the property must be placed in service.
While there might be some uncertainty as to the definition of “installation”, obviously there is a lower standard for claiming a residential credit vs a commercial credit where the term “placed in service” is used. Without researching the legislative history, it appears congress intended to give individuals a greater incentive to go solar by setting a lower standard.
In fact, section 25D drops the bar a notch further for the residential credit in stating an “expenditure” is made when installation is completed; meaning the credit is allowed if the installation is completed in year one while payment is made in year two.
In regards to the term “installation”, let’s say you put a new engine in a semi-truck and the work was completed by December 31,2022. However, the truck was not licensed and permitted until January of the next year. Depreciation on the engine cannot begin until placed in service in 2023.
Now what if tax code said depreciation could begin when “installation is completed”, would you tell client no depreciation until ready and available for service? Or would you start depreciation in year engine was physically installed instead of waiting until the next year when permits were obtained?
Getting back to OP, I would have this discussion (and document it) with client and let them decide if they met the definition of “installation”.