According to the European Standard, modification is defined as:
The combination of all technical, administrative actions, intended to change one or more functions of an object.
For maintenance, this means all measures designed to improve product quality or speed. This also applies when a piece of equipment is modified to suit a new product or packaging. Such measures should be separated in terms of cost from the maintenance budget and they are usually expensed as investments.
The standard states that:
OVERHEAD COSTS OR INVESTMENT?
Sometimes it can be difficult to determine if a scheduled activity should be expensed as an investment (modification) or as an overhead cost. The chart below is intended to serve as an aid in the face of similar issues.