What is a Requirements Traceability Matrix (RTM)?
The requirements traceability matrix is a table linking every requirement to its origin (business need, stakeholder, regulation) and forward to the deliverable and test that proves it was met. Each requirement gets a row you can trace end-to-end: where it came from, where it's built, how it's verified.
Its two superpowers: nothing gets silently dropped, and nothing gets silently added. If a requirement can't be traced back to a business objective, it's a candidate for removal — the RTM is one of your best anti-scope-creep tools.
Worked example
In a medical-device software project, requirement REQ-047 ("audit log retained 7 years") traces back to an FDA rule and forward to database module DB-3 and test case TC-112. At the audit, the team answers "prove you handle retention" in thirty seconds by pointing at one row.