Gwinnett County residents accustomed to paying their property taxes in two installments will make a single payment this year.

In the past property owners usually paid half their tax bill on Sept. 15 and half on Nov. 15. This year the entire amount is due on Nov. 15.

Tax Commissioner Richard Steele said most property owners shouldn’t notice the change because they pay their tax bills through their mortgages. But the 40 percent of property owners who pay directly -- roughly 110,000 owners -- will have to adhere to the change.

County officials said a new state law that pushed back the timeline for tax collections is responsible.

Last year the General Assembly passed Senate Bill 346, which requires counties to send every taxpayer a notice of their property’s value each year. Previously, counties sent notices only if the value changed.

The law also gave taxpayers 45 days to appeal their appraisal -- up from 30 days -- and made other changes to the assessment process.

As intended, the law led to a big increase in appeals by owners who felt the county had not assessed their property accurately. Gwinnett residential and commercial appeals more than tripled this year to 31,095.

Gwinnett Chief Appraiser Steve Pruitt said the calendar changes and the higher appeals workload have pushed back the county’s timeline for mailing tax bills and collecting payments. Instead of setting a tax rate in mid-June, county commissioners are scheduled to set the rate on Aug. 2. And the tax commissioner’s office plans to mail tax bills Sept. 15 instead of July 15.

State law gives taxpayers 60 days after the bills are mailed to pay them. So the earliest Gwinnett can collect property taxes is Nov. 15.

County Commission Chairwoman Charlotte Nash said a single bill is needed to ensure governments, especially the school district, collect the tax money in 2010 to maintain adequate cash flows.

Nash said county officials will see how the new single-payment billing goes this year before deciding whether to continue it next year.