Washington's higher taxes have driven the District's largest savings and loan to move its headquarters across the Potomac into Virginia.

Columbia First Federal Savings & Loan Association has signed an office lease in Rosslyn and expects to complete the move -- which will involve 275 workers -- by the end of the year, Columbia First Chairman and President Dewitt T. Hartwell said yesterday.

The move is the second relocation of a major S&L from the District to Virginia in five years. Perpetual Savings Bank, then the largest S&L in the District, moved its headquarters to Alexandria in 1982, in part because of dissatifaction with city taxes and laws restricting S&L branching. It comes despite years of effort by the city administration to step up efforts to attract and keep business in the District.

Columbia First made the decision in recent weeks after spending months weighing the advantages of the District, Maryland and Virginia, Hartwell said. Moving to Virginia will save the S&L "tens of thousands" of dollars a year, according to Columbia First officials.

Hartwell and other executives said the move was prompted initially by Columbia First's having outgrown its headquarters on 13th Street NW. "The driving force was the sheer lack of space," Hartwell said.

But once the company knew it had to move, he said, it was obliged to compare the cost of office space and taxes in the District with surrounding areas. The District didn't compare favorably.

The corporate tax rate in D.C. is 10.5 percent of earnings. Virginia's rate is 6 percent, according to Columbia First officials. The District's unemployment tax is 1.5 percent. Virginia's is 0.22 percent, the officials said. The officials said they could not calculate the exact amount that Columbia First would pay in total D.C taxes this year. But they did say that for the first nine months of the year, the company expects to have paid $37,000 in unemployment tax alone.

Taxes are taken out of earnings, cutting directly into the bottom line.

Columbia has assets of $1.82 billion and 26 branches in the District and surrounding suburbs. Hartwell said customers will not notice any change in service because of the planned move. "We'll still be serving the District and be very involved here," Hartwell said.

District officials had no comment yesterday.