Asset-Backed Security

Securitization begins with a true sale: the originator transfers a defined pool of receivables to a special purpose entity, legally isolating the assets so that a later bankruptcy of the seller does not pull them back into the estate. The SPE funds the purchase by issuing notes, and a servicer, often the originator itself, continues to collect payments and pass them through.

Collections are then distributed by a contractual waterfall. Fees and servicing come first, then interest to the most senior notes, then interest and principal down the capital structure, with residual cash to the equity or seller interest. Tranching is what allows a pool of subprime auto loans to support a high-rated senior class: the senior notes are insulated because losses hit the bottom of the stack first.

Internal enhancement is built from the deal's own cash flows. Subordination means junior classes absorb losses before senior ones. Overcollateralization means the face value of the pool exceeds the notes issued, so the collateral can shrink before the liabilities are impaired. Excess spread is the difference between the yield on the receivables and the coupon plus fees paid out; it is the first line of defence and is consumed monthly before any tranche suffers. Reserve accounts hold cash set aside at closing or trapped as the deal seasons.

External enhancement, such as a third-party guarantee or surety wrap, links the rating to the guarantor's own creditworthiness. That linkage proved fragile when monoline insurers were downgraded during the financial crisis, and market reliance on it has since fallen sharply.

Collateral type drives structure. Auto loans, equipment leases and student loans are amortizing: borrowers pay scheduled interest and principal, so the pool self-liquidates and note balances decline. Credit card receivables are non-amortizing; balances revolve, so the deal typically has a lockout or revolving period during which principal collections buy new receivables and investors receive interest only, followed by a controlled or bullet-like accumulation period that repays principal.

Revolving deals carry early amortization triggers. If excess spread turns negative, delinquencies breach a threshold or the seller fails, principal is turned over to investors immediately, shortening the notes and protecting them from deteriorating collateral. Prepayment and default both accelerate cash flows in amortizing pools, which is why weighted average life, not legal final maturity, is the relevant horizon measure.

Expect to identify the parties in a securitization and explain why bankruptcy remoteness makes pool credit quality, not originator credit quality, the driver of the rating. Be able to rank tranches by loss position, describe how subordination, overcollateralization and excess spread each absorb losses, and compute a simple enhancement level as protection available divided by the initial pool balance.

Distinguish credit tranching from time tranching, the latter allocating principal by sequence rather than by loss. Recognise the structural difference between amortizing and revolving collateral, the purpose of early amortization triggers, and why ABS spreads widen with expected pool losses and with liquidity stress. On statements, understand that consolidation rules determine whether the SPE's assets and notes appear on the sponsor's balance sheet.