Hi All, when should we apply for writ? I have been stuck in security screening since April. I submitted my application in December and still have not passed background and prohibitions.
Well, once the processing of your application is "significantly" longer than expected. In your case, you applied 10 months ago, which isn't crazy long yet (average processing time was 11 months mid 2023 after all) and is probably still too soon. Maybe 18 months or 2 years starts getting mandamus territory, but to really answer your questions, it's better to have a first consultation with a lawyer, who should tell you when to apply based on your own situation.
Meanwhile, make sure you explored all others ways of speeding up the process (webforms or phone calls with IRCC, contacting MP...)