Concerns that a highly-critical ombudsman's report on the corporation that oversees assessment in the province could provoke an onslaught of last-minute tax appeals by property owners has moved the province to extend the deadline for such appeals by 90 days.

Ombudsman Andre Marin said in his report, titled "Getting it Right and released Tuesday morning, that the Municipal Property Assessment Corporation (MPAC) has a "superiority complex," and has often ignored successful appeals against its decisions.

His report went on to say the assessment corporation withholds information from property owners. And when homeowners appeal their taxes, the onus or burden of proof falls on them to prove the assessment is wrong, he added.

That, he said, is "a David and Goliath battle.

"This is not a matchup, this is a slaughter. And it's happening in tens-of-thousands of cases every year."

Reacting to the report, Finance Minister Dwight Duncan announced that Friday's deadline for appeal would be extended by 90 days. He will introduce legislation to that effect on Wednesday.

The property assessment corporation was formed in the late 1990s to prepare assessment rolls for all Ontario municipalities, plus supplementary assessment lists used to work out taxes on new construction.

Those who disagree with their assessment can appeal to the separate Assessment Review Board. But Marin said even that process works against citizens because MPAC ignored the subsequent rulings.

Marin did say that MPAC has agreed to accept or study most of his recommendations, especially when it comes to giving homeowners more information on what their assessments say – such as whether it incorrectly states there is a three-car garage rather than none at all – in order to prevent errors.

with files from Canadian Press