A valuation roll revised twice is a municipality admitting error.

What does it mean when a municipality changes the value of the same property twice in one valuation cycle? Usually that the first number was not built on enough evidence to stand on its own.

Municipalities compile a general valuation roll every few years, and in between they issue supplementary rolls to pick up new buildings, subdivisions and other changes. That part is normal. A new double garage or a subdivided stand should show up, and the value should move. But when nothing physical has changed and the value still moves twice, the change came from the office and not from the property.

Owners get a window to lodge an objection after a roll is published, and a valuer can revise a value after considering it. When an owner objects and the value drops, and then a later correction moves it again, the municipality is in effect saying its earlier figures were off. Rates are worked out from the value on the roll, so every correction becomes a different rates bill, and often an adjustment backdated on the account.

The practical effect is that the number on the roll becomes something owners argue about instead of something they rely on. And once a few owners on a street have had their values changed on objection, the neighbours start to wonder what their own value is built on.