In my case, TSP was aware that I was separated about the same time I received my first monthly pension check from OPM; about 31 days after I retired. I believe it’s your employing agency that notifies TSP that you’re separated. This occurs when they send your retirement package to OPM. I noticed I could perform unique functions at the TSP online site, like change my address, or apply for a withdrawal as a separated participant. Only separated employees can perform these functions online. About six or seven weeks after I retired, I received a letter from TSP notifying me that I was reported as separated.
Form TSP-77 is used for a partial withdrawal of funds, and form TSP-70 for full withdrawal, for civilian employees. If separated military, the forms are TSP-U-77 and TSP-U-70. Prior to the recent phishing attack, you would fill these forms online by clicking the Withdrawal button. I’ am unsure if this is still possible.b