Basic Checks guidance
https://www.gov.uk/government/publications/basic-checks This is the main guidance page for Basic DBS checks.
https://www.gov.uk/guidance/rehabilitation-periods This document has a table explaining rehabilitation periods.
https://www.gov.uk/government/publications/dbs-check-eligible-positions-guidance All the leaflets produced are on this page or you can follow the links below for specific guidance:
Eligibility guidance for standard and enhanced checks
https://www.gov.uk/government/publications/dbs-guidance-leaflets This page looks at the roles eligible for a standard check. Some of these will also be eligible for enhanced checks.