Structured Finance 2026

Advanced Tutorial on RMBS, CMBS, and ABS Pricing Models. Master the mechanics of credit enhancement and stochastic valuation in structured finance.

Overview

Structured finance is the financial engineering process of transforming illiquid, heterogeneous cash flows into tradable securities through tranching, credit enhancement, and stochastic modeling.

Securitization Fundamentals

Special Purpose Vehicle (SPV): Ensures bankruptcy remoteness and true sale, isolating collateral from originator credit risk.
Tranching & Waterfall: Cash flows are distributed sequentially (Senior to Subordinated). Senior tranches receive lower yield but highest priority. Equity/Residual absorbs first losses.
Credit Enhancement:
- Subordination: Junior tranches absorb losses before senior tranches are impaired.
- Overcollateralization: Asset pool par value exceeds securities par value.
- Excess Spread: Difference between collateral WAC and securities WAC, trapped in reserves.

RMBS (Residential Mortgage-Backed Securities)

Agency RMBS: Guaranteed by GSEs (Fannie, Freddie, Ginnie). Zero credit risk but high prepayment risk.
Non-Agency RMBS: Private-label securities requiring credit enhancement.
Prepayment Modeling:
- PSA Curve: Benchmark for measuring prepayment speeds (CPR/SMM).
- Refinancing S-Curve: Prepayments accelerate rapidly when rates fall 50-100 bps below WAC, but flatten out due to burnout effect.

CMBS (Commercial Mortgage-Backed Securities)

Underwriting: Non-recourse loans underwritten based on property cash flow (DSCR) and equity cushion (LTV).
Prepayment Protection: Unlike RMBS, CMBS have structural barriers to refinancing:
- Lockout Period: Absolute prohibition on prepayment.
- Yield Maintenance: PV penalty for lost interest.
- Defeasance: Substituting collateral with Treasury securities.
CMBS behave more like corporate bonds due to stable duration and lack of negative convexity.

ABS (Asset-Backed Securities)

Auto Loans: Short duration (3-5 years), predictable cash flows, minimal prepayments.
Credit Cards: Master trust structure with a revolving period where new receivables replace paid-off balances.
Student Loans: Long duration (10-20 years), high prepayment variability.

Monte Carlo Valuation Framework

Structured finance securities with embedded options require path-dependent pricing:

Interest Rate Simulation: Generates paths using short-rate models (Vasicek/CIR/Hull-White).
Prepayment & Default Model: Estimates prepayments and defaults dynamically for each path.
Cash Flow Engine: Routes payments through the deal-specific structural waterfall.
Option-Adjusted Spread (OAS): The pure credit and liquidity premium after removing interest rate risk and embedded options. RMBS exhibit negative convexity (prices rise less when rates fall than they fall when rates rise).