Asset-Backed Securities

The exam usually tests two things: what distinguishes ABS from mortgage-backed securities (MBS), and why the SPV structure matters for investor protection.

How Do ABS Work?

• Structure is similar to mortgage-backed securities (MBS) (pooling and tranching)
• Interest and principal payments from the underlying asset pool pass through to investors
• Subject to credit risk of the underlying borrowers and prepayment risk
• Typically structured with credit enhancements (overcollateralization, reserve accounts, subordination) to improve ratings

Think of it this way: Imagine a bank has 10,000 auto loans on its books. Instead of waiting years for borrowers to repay, the bank bundles those loans, sells them as bonds to investors, and gets cash immediately to make more auto loans. Investors get a stream of payments from the underlying borrowers.

What Is a Tranche?

A tranche is not just an abstract slice of cash flow: it is a separate security in its own right. When the SPV issues the ABS, it typically splits the deal into multiple tranches, and each one is its own bond with its own coupon rate, credit rating, and place in line for repayment. A typical deal issues three:

• Senior tranche: paid first, carries the highest credit rating, and pays the lowest yield because it carries the least risk.
• Mezzanine tranche: ranks below senior and above junior in both credit rating and priority of payment, and pays a yield in between.
• Junior tranche (also called the equity or residual tranche): paid last and absorbs losses first, so it pays the highest yield to compensate investors for that risk.

An investor picks a tranche to match their own risk tolerance: a risk-averse investor buys the senior tranche for the lower yield and higher safety, while an investor chasing yield buys junior and accepts first exposure to losses.

How Do Credit Enhancements Work?

Overcollateralization, reserve accounts, and subordination all work the same way: they build a buffer that absorbs losses before those losses reach investors, particularly senior tranche holders.

• Overcollateralization: the pool holds more collateral (loan principal) than the amount of securities issued against it. If $110 million of auto loans backs $100 million of ABS, the extra $10 million of collateral absorbs the first losses before any bondholder is affected.
• Reserve accounts: cash set aside specifically to cover shortfalls, either funded upfront at closing or built up over time from "excess spread" (the gap between the interest collected from borrowers and the interest owed to investors). If a month's borrower payments come up short, the reserve account covers the difference.
• Subordination: the ABS is split into tranches ranked by seniority. Junior (subordinate) tranches absorb losses first; senior tranches are paid in full before any junior tranche takes a loss. This is why a senior tranche can carry a higher credit rating than the underlying loan pool would otherwise support on its own.

Think of it this way: subordination works like floors of a building during a flood. The ground floor (junior tranche) takes on water first, and the upper floors (senior tranches) only flood once the lower floors are completely submerged.

Exam Tip: Gotchas

• Credit enhancements protect against losses (credit risk). They do not change when investors get paid; dividing cash-flow timing into tranches with different average lives is a separate structuring technique, tested on its own.

What Is Securitization and the Special-Purpose Vehicle (SPV)?

Securitization is the process of pooling financial assets and issuing new securities backed by those assets. ABS are the result of securitization applied to non-mortgage receivables.

The special-purpose vehicle (SPV) is the legal entity that:

• Receives the pooled assets from the originating bank or lender
• Issues bonds (the ABS) to investors
• Collects payments from the underlying borrowers and passes them through to ABS holders

The SPV is bankruptcy-remote from the originator: even if the originator fails, the assets in the SPV remain dedicated to ABS investors.

Securitization sequence:

1. Loans are originated by a bank or lender (e.g., auto loans, credit card receivables, home equity loans)
2. The originator transfers the pooled loans to an SPV
3. The SPV issues bonds (the ABS) to investors, raising cash
4. Borrowers make payments on the underlying loans
5. Cash flows pass through the SPV to the ABS holders as interest and principal

Selling the pool to the SPV also frees up the originator's own capital, since the loans move off its books, letting it make new loans instead of waiting years to collect on the old ones.

Exam Tip: Gotchas

• ABS are backed by non-mortgage assets (auto loans, credit cards, student loans, home equity loans). MBS are backed by mortgages. The exam may test whether you know the difference. Both are subject to prepayment risk.
• The SPV is a separate legal entity, not a department of the originating bank. That separation is what makes the ABS bankruptcy-remote from the originator.

What Should You Check on Exam Day?

• ABS are backed by non-mortgage assets; MBS are backed by mortgages
• The SPV isolates ABS investors from the originator's credit risk (bankruptcy remoteness)
• ABS are split into tranches (senior, mezzanine, junior) that each carry a different rating and yield
• Credit enhancements (overcollateralization, reserve accounts, subordination) improve ABS ratings
• ABS carry both credit risk of the underlying borrowers and prepayment risk