Arlington will become next year the last jurisdiction in Northern Virginia to implement a plan allowing small businesses to pay their county business taxes on an installment plan.

The plan, approved unanimously last night by the Arlington County Board, allows retail merchants, restaurants and filling stations now paying less than $5,000 in business license taxes -- an estimated 919 businesses in all -- to pay their taxes twice a year rather than in lump sum payments each Jan. 31.

The plan was a scaled down version of one proposed by the Arlington Chamber of Commerce, which has been lobbying for relief for local businesses faced with heavy competition from surrounding areas.

The board rejected a third proposal last night, suggested by the county's fiscal staff, to further limit to the tax relief to those businesses paying less than $2,500 in business taxes.

"This is really a small step," said Board Chairman Stephen Detwiler. "To do anything less would be to not make the kind of beginning this board should take."

By delaying the collection of approximately $465,000 until June 15, the county itself will have to pay an extra $17,600 in additional interest charges and raise its bond authorization requirements by $500,000.