Migration Validation & Parallel Run — Runs the old and new billing systems side by side on the same inputs and compares every invoice line before cutover. It is the safety net for data migration — discrepancies route back for correction before the legacy system is retired.
Migration Validation & Parallel Run lives in the Fulfill & Activate phase of Fulfill & Bill — the stage where you activate what was sold, meter what's used, bill it right. In the corpus tool index this phase maps to the Entitlements and Billingcategories.
No product category maps cleanly onto this module yet — companies typically build it in-house or cover it with adjacent tooling. See who builds vs buys across the corpus.