The GM calls for an ability check when you attempt a task (other than an attack) that has a chance of failure. (77) 

 

For each check, the GM decides:

​

• which ability is relevant to the task at hand;

• whether a skill is applicable; and

• (for most tasks) the task's Difficulty Class (DC).

​

Your ability check = d20 + relevant ability modifier + proficiency bonus (if any) + other bonus or penalty.

​

• Roll 2d20 if you have advantage or disadvantage; see the possible reasons for this. 

• Add your proficiency bonus if a skill applies and you are proficient in it; otherwise roll without the bonus.

​

You succeed when your ability check total ≥ the DC. Otherwise you fail.