Contrary to a common misconception, a protest is not always timely if filed within 10 days of a debriefing. As one prospective protester learned, if the debriefing is not ârequiredâ under applicable law, a GAO protest filed within 10 days of a debriefing might be untimely. GAO regulations set specific (and strict) protest filing deadlines. Protests relating to improprieties in the solicitation itself, for example, must be filed before the bid opens or the time set for receipt of initial proposals. 4 C.F.R. Â§ 21.2(a)(1).