Does haste allow a creature to attack and activate tap abilities the turn it enters the battlefield?

Normally, a creature is affected by a rule informally called 'summoning sickness': it cannot attack or activate abilities that include the tap symbol (or untap symbol) in their cost unless it has been under your control continuously since the beginning of your most recent turn. This rule is found in CR 302.6.

Haste (CR 702.10) is a keyword ability that explicitly overrides this restriction. A creature with haste can attack and can activate tap or untap abilities the turn it enters the battlefield under your control, as though you had controlled it since the beginning of the turn.

It is important to note that haste only bypasses the summoning sickness rule. It does not allow a creature to attack during phases other than the combat phase, and it does not exempt a creature from other restrictions such as being tapped, being affected by a 'this creature can't attack' effect, or needing to wait for an ability to reset (like those requiring the creature to have been in play at the start of combat).

Example: You play Goblin Guide (which has haste) on your turn. Because it has haste, you can immediately declare it as an attacker during your combat phase and also activate any tap abilities it might have — all in the same turn it entered the battlefield.