The town of Prompton, Pa., supposedly earned its name because its inhabitants always paid their bills on time. The tradition certainly continues. Judith Knash, director of the Wayne County Tax Claim Bureau, said that there weren't any Prompton residents on the bureau's list of property owners who hadn't paid their 1988 taxes by the Feb. 28 deadline. Prompton, which has 142 taxable parcels this year, had no delinquent taxes in 1981, Knash said. None of the 27 other tax districts in the northeastern Pennsylvania county could claim a similar record since the tax bureau was created in 1976, she said. "The trend here has been increasing numbers," she said. Delinquencies countywide have risen from 6,124 in 1983 to 6,608 in 1987, she said.