If a partly completed project is put on hold (deferred project) by the client, when it is restarted it should be treated as a new project.
This includes reviewing and redeveloping the scope, project plan, schedule, and budget.
The original project team may not be available anymore, so new people will take time to get familiar with the project.
The project should be renegotiated with the client.
Make sure language in the original contract does not say that no additional costs are allowed due to delays, as the client may use that clause to refuse to renegotiate the price.