OPINION
The appellants are the Tax Claim Unit of Northampton County. They were charged with negligence in failing to notice a resident of her redemption rights following a tax sale of her property. The property was put to sale for delinquent taxes and sold to the appellees. Subsequently, because of the negligent failure of the appellants to give notice, the sale was voided. The appellees brought suit against the taxing authority claiming damage for loss of interest on the amounts they borrowed to buy the property at the sale. The common pleas court accepted their argument that they were entitled to both interest on the funds in *232 the possession of the tax authority and $907.00 for the interest they paid on the money they borrowed. The trial court gave both the interest earned and the interest lost. In view of our holding, little more need be said.
The tax claim unit has raised their governmental immunity for the first time on appeal. They claim they are not only immune but that their immunity is not waivable, even if they negligently failed to do so before. Perhaps here is one reason their immunity cannot be waived; a governmental agency cannot be put at the mercy of negligent or agreed waiver by counsel of a substantive right designed to protect its very existence. Such negligence can spread, pebble in a pond, until the governmental agency would be engulfed in a tidal wave of liability. This Court in
Mayle v. Pennsylvania Department of Highways,
*233
The order of the Commonwealth Court,
