The date of completion is the date the property is available for occupancy.

With a single family home the entire improvement will become available for occupancy within a reasonable short period of time. It will be considered as under construction until all portions of the home are available for occupancy by the appropriate government official, the contractor has fulfilled all of the contractual obligations and the customer has met all financial obligations.

At that time the customer will receive a Certificate of Occupancy and will be allowed to move in.

Do you have a question for the builder?  If so, please ask in the comments below.