As the paladin ability.
Prerequisite: Base attack bonus +1.
Benefit: Once per day, you may attempt to smite evil with one normal melee attack. You add your Charisma bonus (if any) to your attack roll and deal 1 extra point of damage per character level to a maximum of +4. If you accidentally smite a creature that is not evil, the smite has no effect, but the ability is still used up for that day.
Prerequisites: Base attack bonus +5.
Benefit: Twice per day, extra damage maximum of +9.
Prerequisites: Base attack bonus +10.
Benefit: Three times per day, extra damage maximum of +14.
Prerequisites: Base attack bonus +15.
Benefit: Four times per day, extra damage maximum of +19.
Prerequisites: Base attack bonus +20.
Benefit: Five times per day, extra damage maximum of +20.