The Government Accountability Office signed a tentative agreement with union officials Friday, a big first step for the agency’s first-ever union. The agreement only concerns employees’ pay raises for 2008, a priority for a union that was created partly because of a controversial switch to a market-based pay system. It would give every employee that gets a “meets expectations” rating the full 4.49 percent raise of other local federal employees. Now, union members will have to vote on the agreement before it can go into effect. The union will distribute e-mail ballots on Monday. They must be returned by Feb. 14. — Emily Yehle