Arlington County property owners may want to start saving now, because if current projections hold, the owner of an average single-family home may pay $330 to $440 more in taxes next year, county officials estimate.

That estimate is loaded with conditions, and the biggest one is that it’s almost six months between now and when Arlington typically passes its annual spending plan. But county budget officials told a joint meeting of the County Board and School Board last week that even without a tax rate increase, assessments on single family homes are expected to go up about 8 percent, and condos up 5 percent, which means that the $5,505 in taxes on the average $552,700 Arlington residence would also rise.

“We’re a long way from knowing what the actual projections are,” Jay Fisette (D), County Board chairman, said Wednesday. “We have options, and we have to look at what the requests and needs are.”

The County Board is scheduled to give County Manager Barbara Donnellan its guidance Tuesday on which priorities it wants in its next budget. Actual property assessments are firmed up in January, and then Donnellan typically presents her proposed budget in late February. The board usually sets the property tax rate and passes the budget in late April.

Last spring, the County Board trimmed its tax rate to $0.996 per $100 of assessed valuation, down from $1.006 per $100. But residential assessments rose by an average of 5.3 percent, which meant that most homeowners saw higher tax bills this year.

Arlington takes a conservative approach to budget projections, but even by those standards, it appears the county has come out of a difficult year in which the after effects of the federal government shutdown and federal budget cuts known as sequestration shook its financial foundations.

Its residential real estate market is solid, although the commercial vacancy rate rose above 20 percent this year. Since the source of Arlington’s tax revenues are evenly split between homeowners and commercial property owners, weakness in either sector negatively influences the other. County revenue is expected to grow, but spending is expected to be no more than $10 million higher, according to a presentation made at the Nov. 7 County Board-School Board meeting.

Arlington’s schools, with booming enrollment, expect a budget shortfall of about $28 million, despite the $106 million school bond issue that 75 perent of Arlington voters approved last week. About half of Arlington County’s budget goes toward paying for schools.