The notification flashed at the top of my screen in bold, white text. But I hadn't fired a shot in five minutes.
For example, if a player joins a game wielding a weapon from the "Gage Mod Courier" pack, but the game detects they do not own that DLC on their Steam account, the Cheater Tag is applied. Other triggers include manipulating skill point counts, carrying an impossible amount of deployables (like having 14 doctor bags on a single character), or altering loot values during a heist. If you have been using "unlocker" mods to bypass paid content, you almost certainly carry the tag. Payday 2 How To Know If You Have A Cheater Tag