Best practice for construction revenue recognition when costs under- or over-run budgets

Hey, gang - I’ve got a client set up to recognize revenue for a fixed price project with periodic billing that needs to recognize 100% of the revenue at the end of the project, but I’m curious as to what the best practice is in the likely scenarios when 

1.  The project is complete and the actual cost(s) do not meet the corresponding budgeted amount(s) and
2. The opposite situation where the actual costs exceed the budgeted amounts.

Respectively, what would be the most effective process for recognizing the balance of unrec’d revenue and also setting limits on how much revenue can be recognized?  Thank you in advance!