Fulton County has flubbed up again in its legal duty to let residents know how much in property taxes they can expect to pay.

The county told nearly 30,000 Roswell taxpayers last week to prepare to shell out 10 times the amount of city taxes they will actually owe. The cause: A staffer in the assessors office misplaced decimals in the city’s tax rates, Chief Appraiser David Fitzgibbon said.

The errors, contained to Roswell, appeared on assessment notices that began arriving in mailboxes Monday. Under Senate Bill 346, a homeowners’ rights measure pushed in 2010, counties must inform all taxpayers of their property values for tax purposes and provide estimated bills, including city taxes.

Because these were notices and not actual bills, they have no impact on something like a mortgage escrow account.

William Jones’ assessment notice told him he’ll owe $7,868 to Roswell. It gave him a jolt, but then he did his own calculating and came up with the correct figure: $786.80.

“It does give you lack of confidence that whatever they send you might not be accurate,” Jones said. “This whole idea about having another county, going back to Milton, maybe that makes sense because Fulton County treats us like we’re just idiots.”

It’s yet another blemish for the department, which has struggled to comply with SB 346 in the past and is frequently accused of overvaluing home values, which determine tax bill amounts.

Fitzgibbon apologized for the latest mistake. He declined to say who made it but said he’s accountable as the department supervisor.

“I take full responsibility for it,” Fitzgibbon said. “It’s something we regret and certainly embarrassing, but in the end it’s going to have zero effect on what people are going to pay.”

The blunder hearkens to 2011, when Fulton sent overblown tax estimates to about 136,000 Atlanta taxpayers, attributed to a formula error affecting solid waste charges.

The county also left out municipal tax estimates in 10 cities and wound up remailing 230,000 notices, costing about $140,000 and pushing back the appeals deadline by five weeks for 70 percent of the county.

This time, the Board of Assessors has opted not to mail corrected notices. Not only would that cost as much as $15,000 in postage, printing and processing, but it would push the 45-day appeal deadline back for Roswell and complicate the online filing system.

Since all appeals must be in before the tax digest can be certified by the state, that would cause tax bills to go out about a month late and have the county, school systems and some cities waiting longer to collect revenue.

Though this error affects fewer people than the Atlanta fiasco, it’s significant. Some Atlantans had thousands of dollars tacked onto their estimates; Roswell’s estimates are multiplied by 10.

Sam Evans got his notice Friday, telling him he’ll be billed by Roswell for $5,605, more than $5,000 too high.

“It’s just terrible,” he said. “I’ve always been disappointed in Fulton County, especially the tax people.”

City Hall averaged 100 calls a day from people complaining this week, a spokeswoman said. Roswell Mayor Jere Wood wants Fulton County to reconsider sending corrected notices.

“Some of us can take this lightly, but if you happen to be an old person who doesn’t understand these things, it could cause you to panic, lose a lot of sleep,” he said. “That’s not good service.”

No similar errors have been reported this year in Cobb, DeKalb or Gwinnett counties. Gwinnett had a similar case last year when close to 1,500 notices went to Buford residents omitting the homestead exemption. The county sent out corrected forms and restarted the appeals clock.

Fitzgibbon said Roswell taxpayers can get corrected notices by the middle of next week by looking up their properties on FultonAssessor.org.

They can also just wait for Roswell to send the actual bills later this year.

Tax activist R.J. Morris, who frequently butts heads with the department while representing homeowners in tax appeals, said there might have been time to send new notices had the county not sent them a month later than it did last year. Fitzgibbon cited staff vacancies and a need for quality control and editing.

“You know what I like about it?” Morris said. “It’s going to encourage everyone in Roswell to appeal.”