By Mike Dunn

PHILADELPHIA (CBS) — About one-quarter of all homeowners in Philadelphia may be in a for a surprise — pleasant or unpleasant — this week. City officials on Thursday are mailing them reassessment notices, which will alter their property tax bills next year for better or worse.

Just two years after the city completed a reassessment of every property, they’re doing it again, and Philadelphia Chief Assessor Michael Piper says the notices will go out Thursday: “There are about 125,000 residential units that are getting assessment change notices. Some are being increased, some are being decreased.”

Piper says more than half of the homeowners being reassessed will actually see a drop in their home’s value. “Some parcels are going to be increased (but) I think we can safely say of the 125,000, what we saw are more decreases than increases overall.”

Whether the values go up or down, no neighborhood will be spared. “They’re across the city. Every councilmanic district has some changes. Some increases and some decreases,” says Piper.

This comes two years after the Nutter Administration — amid much controversy — launched a new assessments system dubbed the “Actual Value Initiative,” or AVI. Piper says the original set of values generated under AVI were not perfect, and this reassessment is aimed at moving those values closer to accuracy.

“We need to make sure that everyone’s being assessed fairly, and based on accurate assessments of what a property is worth,” Piper says. “Inaccurate to us, means wrong. Not too high or too low, but wrong. And we’re trying to make it less wrong. If you see an increase in your assessment, it’s because we see that sales indicate that the market value that we were looking at may have been a little low.”

But this won’t be the end of it. The city’s goal is to reassess every property every year.

Its far from clear if the Office of Property Assessment — with limited manpower — could actually achieve that. And some members of City Council have already voiced misgivings about frequent reassessments, and the fear they strike in the hearts of longtime homeowners.

Councilman Mark Squilla proposes reassessments of one-quarter of the city each year, so individual homeowners would only face these notices of changes in value once every four years. Whether annual assessments or something like Squilla’s plan become reality may depend on the stance of the next mayor.