Last week, tens of thousands of Atlanta homeowners opened envelopes from the Fulton County assessors office and read that their tax bills would shoot up by thousands of dollars this year, resulting in some stiff drinks and sleepless nights.

Chief Appraiser Burt Manning, whose office sent out about 333,000 tax assessment notices countywide, assured them it was a calculation error. A commercial solid waste charge that should have been applied to some Atlanta properties was applied to the majority of Atlanta properties, he said.

It’s a major foul-up, considering the city’s 140,000 parcels make up about 40 percent of the county.

Here are some questions that might be on Atlantans’ minds:

Q: Is my assessment also incorrect?

A: No. Manning says there is nothing wrong with the appraised home values printed on the notices (though taxpayer advocacy groups would take issue).

Q: Should I appeal to avoid paying the inflated amount?

A: No. The actual bills going out later this year should tally taxes correctly. For an accurate estimate, Manning says, disregard the bottom line on the notices labeled “total estimate” and re-tally county, city, school and state taxes. Be careful not to add in subtotals. Because of a moratorium on assessment increases, most people’s taxes should be going down or staying the same.

Q: Was anything else incorrect on the notices?

A. Yes. The estimated taxes also used last year’s homestead exemption of $25,000, instead of using this year’s figure of $30,000. The exemption is a tax break for homeowners who live at their properties, and the increased amount should mean slightly lower taxes, so long as millage rates don’t go up.

Q: Whose fault is this?

A: On the incorrect estimates, evidence points to county staff. While contractor Tyler Technologies Inc., which sold the county the software, hasn’t been ruled out as the culprit, Fulton Information Technology Director Ryan Fernandes said he doubts it. Manning concedes that his staff should have sampled more mailings before sending them out en masse. On the homestead exemptions, Manning said his office lacked data tables with the new figures, so he used last year’s figures rather than leaving out exemptions altogether.

Q: Can this be fixed?

A: The county spent all week getting word out that the estimates on affected bills can be disregarded, with Manning taking part in a live Twitter chat Wednesday. If the county opts to send letters with corrected estimates, it could cost taxpayers about $50,000 to $60,000, not including labor and overtime.

Q: Who should file appeals?

A: Anyone who disputes the “current year value” printed on the notices. That’s the figure that will be calculated with millage rates and exemptions to determine tax bills.

Q: Does the 45-day deadline listed on notices still apply for filing appeals?

A: Yes. Unless the assessors office sends out new notices altogether — which appears unlikely — the deadline remains June 21.