How does this question arise in your case, bob? Just curious; overage is not something encountered very often when someone buys a property. Terms of it vary a good deal, generally dependent on the state of the market at the time of its creation. It may be as low as 30 per cent for 20 years duration or as high as 50 per cent for 50 years, being the percentage of the increase in value and the period in which the overage can be claimed.