Yes you pay tax on dividends and interest even if it was reinvested. A reinvested dividend is really 2 transactions, a dividend and then a buy. Like if they sent you a dividend check and you bought more shares. So when you eventually sell some shares don't forget to add the reinvested amounts to your cost so it will reduce any gain.
And this all assumes this is in a regular accounts. Not any 401K, IRA or retirement accounts. Those work differently.
