How do I check my Steam purchase history?

Go directly to store.steampowered.com/account/history/ and sign in. This shows every purchase made through Steam — date, game name, payment method, and amount. For games activated using third-party keys (from sites like GhostKeys or Eneba), check store.steampowered.com/account/licenses/ instead — this shows every product ever activated on your account including external keys.