How often during combat can you be Surprised?

Question

Looking at the rules for Surprise on page 189 of the 5e PHB. It says that a creature is surprised if the enemy's stealth check beats their passive perception. It then goes on to say:

Any creature that doesn't notice a threat is surprised at the start of the encounter

Emphasis mine.

So that's pretty straight forward, you hide, roll stealth and beat the passive perception of the monster and you get a surprise round.

Now I have 2 other scenarios I'm confused about:

1. What if the creature is actively looking and therefore makes a perception roll instead of relying on passive perception? If the stealth check beats the perception check, does the stealth user still get a surprise round? And,

2. What happens when you use the hide action and succeed or turn in visible in combat? Would the enemy presumably lose track of you and be surprised if you attacked from behind?

Answer 1

First, there is no such thing as a "surprise round" in D&D 5e; you've played earlier editions, haven't you?

In 5e, there is only the first round of the combat during which some (or all) of the creatures involved are surprised and some (or all) of them aren't.

The DM determines who might be surprised. If neither side tries to be stealthy, they automatically notice each other. Otherwise, the DM compares the Dexterity (Stealth) checks of anyone hiding with the passive Wisdom (Perception) score of each creature on the opposing side. Any character or monster that doesn't notice a threat is surprised at the start of the encounter.

If you are surprised, you can't move or take an action on your first turn in combat, and you can't take a reaction until that turn ends. A member of a group can be surprised even if other members aren't.

A surprised creature that rolls well enough in the initiative may be over their surprise before anyone else gets to act.

To your questions:

1. That is entirely correct, if the Dexterity (Stealth) beats both the active and passive Wisdom (Perception) score then that creature is surprised (on the basis that actively looking can't make you worse). However, a creature needs a reason to use active perception. A guard on duty for 8 hours cannot be on alert that whole time but if they have heard nearby combat or seen flashy spells ...

2. Surprise happens at the start of the combat, if you hide during the combat the creature has still "noticed a threat". If you were to wait 10 minutes you could probably start another combat though.