Minimum retention requirement limits originator's ability to offload credit risk, mandating retained interest and prohibiting hedging or transfer. Regulation 30B requires the originator to retain a prescribed portion of the book value of securitised assets, with lower retention for short dated cash flows and a specified lower threshold for residential mortgage backed securities. Retention for residential pools must follow an order-first loss facility, then equity tranche, then pari passu in other tranches where needed-and for larger securitisations may be held in first loss, equity or other tranches. Overcollateralisation and certain interest only or excess spread investments do not count. The originator cannot hedge, sell, encumber, or transfer the retained risk to group entities; the form of retention must remain unchanged and be maintained as a percentage of unamortised principal except for repayment or loss absorption.