The Nassau County Department of Assessment in Mineola is shown...

The Nassau County Department of Assessment in Mineola is shown on Thursday, Jan 12, 2017. Taxpayers come to the office if they have questions about their property taxes. Credit: Newsday / John Paraskevas

This year’s candidates for Nassau County executive, comptroller and legislature will have to say how they would handle numerous local problems. One issue, though, dwarfs all the others.

Nassau’s failed tax-assessment system is dragging the county down. It’s the primary driver of the county’s more than $3 billion in debt, as well as budget deficits that exceed $100 million annually. And the candidates who put forward legitimate plans to fix this mess should be rewarded at the ballot box.

A record 216,000 Nassau County property owners filed assessment appeals this year. Traditionally, about three-quarters of appeals win reductions. About 85 percent of those challenging their assessments used tax appeal firms, which generally take about half of the savings realized in the first year after the appeal. Over the past six years, those fees have amounted to more than $500 million.

In the past seven years, 72 percent of Nassau property owners appealed their assessments at least once. Some did it every year. But the reductions don’t change the amount of money the county needs to collect to deliver services. The tax rate simply goes up. So one year you get a reduction, the tax appeal firm gets half your savings, and your neighbor, the one who didn’t appeal, pays more to cover the difference. The next year, your neighbor gets a reduction, the tax appeal firm gets half the savings, and you end up paying more to make up the difference. And the 28 percent who never appeal their assessments get crushed as their tax rate skyrockets year after year to cover the shrinking tax revenue.

In 2010, County Executive Edward Mangano overhauled how residential property tax appeals are handled, settling appeals before the rolls are set (by approving the vast majority of them) so refunds don’t have to be issued. This has saved the county $20 million to $30 million a year. However, because of its unusual “county guarantee,” Nassau has to pay 100 percent of refunds for every school district and municipality, even though it gets only about 16 percent of the overpayments. Mangano also stopped assessing properties, so the only time the rolls change is when taxpayers win reductions. Consequently, the system is way out of touch with realistic values.

The county’s precarious finances lead to cuts in bus routes, youth services and infrastructure projects, as well as growing debt, massive fee hikes and revenue schemes like the red-light cameras. Mangano has a plan to stop much of the bleeding, which comes from commercial property appeals, but it will likely be challenged in court.

There are changes in state law that would help, such as creating a margin of error beneath which refunds would not be due, putting those who appeal at risk of increases if their assessments are found to be too low, and moving assessment out of Nassau’s hands and giving it to the towns. But as things stand, Nassau must build an accurate assessment system and then fight for the valuations it creates.

The candidates have to present credible plans to improve the assessment system, and be judged on them. Because in the long run, if Nassau fails to fix this problem, it’s not going to succeed at all.