What are the different types of credit enhancement in asset-backed securities?

Credit enhancements are structural features that protect ABS investors from losses on the underlying collateral. They fall into two categories: internal (built into the deal structure) and external (provided by third parties).

Internal Credit Enhancements:

1. Subordination (Credit Tranching)

The most common method. The collateral pool is divided into senior, mezzanine, and equity tranches. Losses hit the equity tranche first, then mezzanine, then senior.

Example — Harborview Auto Loan ABS (fictional):

• Senior tranche (AAA): $800M — last to absorb losses
• Mezzanine (BBB): $150M — absorbs after equity exhausted
• Equity (unrated): $50M — first loss position
• Total collateral: $1,000M
• The senior tranche can withstand $200M in losses before being impacted

2. Overcollateralization (OC)

The collateral value exceeds the bond value. If $1,050M in loans backs $1,000M in bonds, the $50M excess absorbs initial losses.

3. Excess Spread

The weighted average coupon on the collateral exceeds the weighted average coupon paid to bondholders. If collateral yields 7% and bonds pay 5%, the 2% excess spread absorbs losses before they reach bondholders.

4. Reserve Account

Cash set aside at closing (or built from excess spread) to cover potential losses.

External Credit Enhancements:

5. Surety Bond / Financial Guarantee

A third-party insurer (monoline) guarantees payment. The bond's rating depends on the insurer's credit quality.

6. Letter of Credit

A bank provides a credit facility that the trust can draw on if collateral cash flows are insufficient.

7. Cash Collateral Account

The originator deposits cash with the trust as a loss buffer.

Exam Tip: CFA Level II tests whether you can identify which enhancement protects which tranche and what happens when losses exceed a specific enhancement level.

Practice ABS structure analysis in our CFA Level II bank.