In a decision that could affect every property owner in Washington, the state Supreme Court Thursday struck down voter-approved Initiative 747.

Here are the answers to questions you may have:

Q: What is Initiative 747?

A: It's a Tim Eyman-sponsored measure, passed by voters in November 2001, that limited property-tax growth to 1 percent a year.

Q: Are my property taxes now going up?

A: It's possible, but not certain. With I-747 out of the way, local governments and taxing districts are free to increase property-tax collections as much as 6 percent a year. However, many local governments didn't collect as much property tax as they legally could under old limits, and they may choose not to do so in the future.

Also, Gov. Christine Gregoire has asked cities, counties and taxing districts to resist increasing taxes based on Thursday's ruling and give the state Legislature time to develop a new property-tax cap.

Q: Would there be any limits on property taxes?

A: Yes. Referendum 47, which I-747 supplanted, is now the law again. That measure, approved by voters in 1997, sets looser limits on annual increases in non-voter-approved property-tax collections. For larger jurisdictions, R-47's cap is the rate of inflation — 2.1 percent for taxes due in 2008 — but that can be increased to 6 percent if two-thirds of the members of a jurisdiction's governing board agree.

Q: Could governments go back now and collect the property taxes that I-747 prevented them from collecting before the ruling?

A: No. But the ruling could be retroactive in a sense.

Under state law, cities, counties or other local governments can "bank" unused property-taxing authority. Under I-747, for instance, if a government used only 0.5 percent of the 1 percent increase authorized by the law, it could reserve the remainder and use it the next year.

King County Assessor Scott Noble says some local governments could contend they had banked much more — the difference between their actual increases and the rate of inflation — for each of the past six years. In addition to seeking an increase of up to 6 percent next year, they could attempt to raise property-tax collections by that "banked" amount as well.

However, the state Department of Revenue says other limits on tax rates make such increases unlikely.

Q: My property taxes went up more than 1 percent this year. Didn't that violate Initiative 747?

A: No. The 1 percent limit doesn't apply to individual property-tax bills. It's a limit on the annual increase in total regular property-tax collections by the state and local governments.

That 1 percent limit doesn't apply to property taxes approved by voters. Those voter-approved levies are the chief reason property-tax bills have been going up, Noble says.

Q: How much money has I-747 saved the typical homeowner?

A: That's impossible to say. No one knows how much local officials would have raised property taxes without I-747.

In Seattle, officials say that without I-747, property-tax bills for the average Seattle home would have been $252 higher this year. And in May the state estimated that I-747 has blocked about $1.6 billion in property-tax increases over the past six years.

Q: If voters passed I-747 in 2001, why are the courts just now getting around to ruling on its constitutionality?

A: While many attorneys said the initiative raised constitutional questions, no one formally challenged it until 2005, when Whitman County, one of only two counties in the state that voted against I-747, and several statewide organizations filed a lawsuit against it. (King County also voted against I-747.)

Staff reporters Susan Gilmore, Eric Pryne and Sharon Pian Chan contributed to this story. Much of the material comes from The Seattle Times archives.