The Defects Notification Period (DNP) is a certain number of day counted from the date of completion of works that allow the customer to notify defects to the Contractor. In the Wind Energy business is usually 12 months, but in principle can be longer (2 years, 5 years, etc.) or shorter.
There are also situations where there are different type of DNP, shorter for not critical items and longer for critical items.
It is usually start from the certified completion of works (the day the Taking Over Certificate is issue). It is interesting to consider that the majority of contract also include a “deemed taking over” – basically a set of circumstances that constitute a “de facto” taking over.
During the Defects Notification Period the subcontractor will probably need to do some minor works to solve the problem listed in the Defects Punch List. If new problems are discovered by the customer, that the contractor is obliged to fix them.
Finally, a point worth mentioning is that the subcontractor is usually obliged to repair also defects not attributable to him (in this case he is obviously entitled to payment via Variation Order).