South Portland property tax bills will go up 20% on average, the city assessor said this week, as city officials zero in on the taxpayer impact of the citywide revaluation and the proposed municipal budget.

Revaluation data for individual residential property owners will be available by the end of the business day Friday online at gis.vgsi.com/southportlandme. The City Council is expected to vote on the proposed $38.9 million city budget next week.

City Assessor Jim Thomas said this week his office is completing its work calculating new residential property values citywide resulting from the first comprehensive revaluation of this scope to occur since 2006. Skyrocketing home sale prices, he said earlier, are forcing officials to raise residential property values citywide to meet state requirements that property values reflect current market prices.

“Since 2017, the world has turned upside down,” he said.

Thomas said after factoring in changes in both residential and commercial property values, he estimates that, on average, residential property values have gone up citywide by about 20%. That means, he said, residential taxpayers can expect this year’s tax bills to go up, on average, by that much. He stressed, however, that values will, as always, vary from one property to another.

His office will have new residential property values available in the city’s database by the end of the business day on Friday, allowing residents to see on the assessor’s website for the first time just what impact the citywide revaluation is expected to have on their bills. His office next week will mail notices to residential property owners with instructions on how to find their specific revaluation information.

The revaluation’s potential impact led City Manager Scott Morelli to send out letters to residents in April warning of the likelihood of large tax bill increases. Since the revaluation affects property values, Morelli and Thomas have both said, the increases will happen even if the current tax rate doesn’t change.

Nevertheless, city officials have been scrambling to find ways to lower expenses for the 2022 budget. Voters last week passed the $54 million proposed school department budget, which Morelli said this week will lead to a 17-cent increase to the tax rate. There will also be a 1-cent increase due to the county budget, but the proposed $38.9 million municipal budget, if approved, will actually decrease the rate by 3 cents, with a net potential tax rate increase of 15 cents. For the owner of a $250,000 home, the new combined budget would amount to an increase to the tax bill of $37.50, but Morelli said climbing property values citywide mean residential tax bills in particular are expected to go up even more.

The council is expected to vote on the budget at its June 22 meeting, but Morelli said even after that the tax rate could still change for the better. Gov. Janet Mills’ revised state budget proposal allows for increased state funding, which Morelli said could filter down to both the school and municipal budgets. There is potential, he said, for the additional funding to cover enough of both budgets that in the end the tax rate would decrease by as much as 8 cents more.

“A lot of caveats here as the state has yet to approve their budget,” Morelli wrote in an email.

Thomas said the revaluation, which covers a period from 2018-2021, is the first of its scope since 2006, but he noted assessors have been occasionally making what he called “modest adjustments” at key periods in the years since, such as during the Great Recession that began in 2007. Such adjustments, however, were not common, and his office is looking to change that. Thomas said he is planning to make smaller adjustments an annual event, which he said will prevent such large increases from happening all at once in the future.