How do securitization structures work — can someone walk through the waterfall with an example?

Question

AcadiFi · Accepted Answer

Securitization is one of those topics where a concrete example makes everything click. Let's build one from scratch.

**Step 1: The Originator Creates Loans**
Harbor National Bank originates $500M in auto loans with an average coupon of 6.5% and average maturity of 5 years.

**Step 2: Transfer to SPE**
The bank sells the loan pool to a Special Purpose Entity (SPE) — a legally separate, bankruptcy-remote vehicle. Even if Harbor National goes bankrupt, the SPE's assets are protected. This is called **true sale** treatment.

**Step 3: The SPE Issues Tranches**
The SPE issues asset-backed securities in tranches with different risk/return profiles:

| Tranche | Amount | Rating | Coupon | Priority |
|---|---|---|---|---|
| Class A (Senior) | $400M | AAA | 4.2% | First |
| Class B (Mezzanine) | $70M | BBB | 6.0% | Second |
| Class C (Equity/First-Loss) | $30M | NR | Residual | Last |

**Step 4: The Cash Flow Waterfall**
Each month, borrowers make payments on the auto loans. The SPE distributes cash in strict priority:

```mermaid
flowchart TD
    A["Monthly Loan Collections
$500M pool @ 6.5%"] --> B["Servicing Fees
(~0.25% annually)"]
    B --> C["Class A Interest
$400M @ 4.2%"]
    C --> D["Class A Principal"]
    D --> E["Class B Interest
$70M @ 6.0%"]
    E --> F["Class B Principal"]
    F --> G["Class C Residual
(excess spread)"]
    G --> H["Reserve Account"]
```

**Credit Enhancement:**
- **Subordination:** Class C absorbs the first $30M of losses, Class B the next $70M. Class A only suffers if total losses exceed $100M (20% of the pool).
- **Excess spread:** The pool yields 6.5% but weighted-average tranche cost is ~4.5%, creating a cushion.
- **Reserve account:** A cash reserve funded at closing provides additional protection.

**Why the SPE Matters:**
The SPE ensures **bankruptcy remoteness** — creditors of Harbor National cannot seize the loan pool. This allows the senior tranche to achieve a AAA rating even if the bank itself is rated BBB.

**CFA Exam Focus:** You'll likely see questions about: (1) the order of cash flow distribution, (2) how credit enhancement protects senior tranches, and (3) the purpose of the SPE structure.

For more structured finance topics, visit our CFA Level II course.

How do securitization structures work — can someone walk through the waterfall with an example?

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Tranche	Amount	Rating	Coupon	Priority
Class A (Senior)	$400M	AAA	4.2%	First
Class B (Mezzanine)	$70M	BBB	6.0%	Second
Class C (Equity/First-Loss)	$30M	NR	Residual	Last