Backlog Refinement is a critical part of good practice in Scrum. Refining the Product Backlog ensures that the Scrum Team has sufficiently defined Product Backlog Items so that Sprint Planning runs more smoothly and without surprises. The more a team refines its Product Backlog the less time they tend to spend in Sprint Planning.

Timebox: Good practice suggests the team spend approximately 10% of their Sprint refining the Product Backlog.