How does solar purchased through a home builder at new construction affect year-end taxes -- is there a deduction/credit, and does the builder provide documentation?

This one belongs with a CPA or tax preparer, but the paper trail starts with your builder, so ask for it up front. When solar comes included in a new construction purchase, the cost of the system is usually itemized somewhere in your builder contract or closing documents, and that documented cost is what a tax professional works from. There has historically been a federal residential clean energy credit tied to the cost of a qualifying solar system, and some states layer on their own incentives. The percentages, eligibility rules, and paperwork change over time, so confirm the current rules instead of assuming last year's numbers still apply. The practical steps: ask your builder for a clear breakdown of the solar cost plus any manufacturer or installer certification documents, then hand the whole package to your tax preparer. They can tell you whether you qualify, what the credit is worth in your situation, and how to claim it correctly.