Generally, buildings must be contributing to a historic district that is listed in either the Virginia or National Registers in order to receive the credit. In general, work can begin on a structure before final listing in the National Register; however, there is risk involved. If, for some reason, the historic district is not listed after the project is completed, any awarded credits would be subject to recapture. If possible, it is a good idea to wait until the listing process is nearly complete and appears to be on-track before doing any substantial work.
There are some differences between the State and Federal Programs in this matter:
State Program: The property must either be determined individually eligible for listing, listed individually, or be in a listed National Register historic district, prior to credits being awarded.
Federal Program: If you complete your project before the Historic District is listed, the Historic District must be listed on the National Register within thirty (30) months of the project’s completion date in order to claim/retain Federal credits.