casemark/structuring-abs-transactions

Structuring Abs Transactions

Designs asset-backed securitization structures with tranche hierarchy, credit enhancement, and cash flow allocation mechanics.

When To Use

• Designing a new ABS issuance and defining the capital structure (tranche count, sizing, and subordination levels)
• Evaluating credit enhancement adequacy for a given collateral pool and target ratings
• Building or reviewing a cash flow waterfall for principal and interest allocation across tranches
• Comparing structural alternatives (sequential pay vs. pro rata, turbo features, reserve account sizing)
• Stress-testing an existing structure against collateral performance scenarios (default, prepayment, recovery)

Inputs To Gather

• Collateral pool data: Asset type (auto loans, credit cards, trade receivables, RMBS, CLO), aggregate balance, weighted-average coupon, WAL, seasoning, geographic/obligor concentration
• Historical performance: Default rates, loss severity, prepayment speeds (CPR/ABS), delinquency migration curves, recovery timing
• Target capital structure: Number of tranches, target ratings per tranche (AAA through equity/residual), desired advance rate
• Credit enhancement parameters: Overcollateralization target, subordination levels, excess spread, reserve account initial deposit and floor, any third-party support (surety wrap, LOC) [VERIFY against current rating agency criteria]
• Waterfall rules: Payment priority (sequential vs. pro rata), interest-first vs. principal-first, trigger events (delinquency, cumulative loss, OC tests), turbo/catch-up mechanics
• Deal economics: Pricing assumptions per tranche, servicing fee, trustee fee, swap costs (if applicable), target equity yield
• Regulatory context: Risk retention requirements (5% vertical/horizontal/L-shaped), Reg AB II disclosure obligations, EU securitization regulation (STS eligibility if cross-border) [VERIFY jurisdiction-specific rules]

Workflow

1. Profile the collateral pool

   • Stratify by key risk dimensions (FICO/credit score, LTV, loan age, geography, obligor size)
   • Compute pool-level statistics: WAC, WAM, WAL, concentration limits
   • Identify data gaps or quality flags that affect structural assumptions

2. Set base-case and stress scenarios

   • Define base-case default curve, prepayment speed, and recovery assumptions from historical analogs
   • Layer rating-agency stress multiples for each target tranche rating (e.g., Moody's Aaa stress = ~3.5x base loss for consumer ABS) [VERIFY current agency multiples]
   • Include prepayment stress (fast/slow) and recovery lag stress

3. Design the tranche hierarchy

   • Size senior tranche to survive the highest stress scenario with full principal recovery
   • Size mezzanine tranches to meet intermediate rating targets with required coverage
   • Residual/equity tranche absorbs first loss — size as the remaining balance after credit enhancement allocation
   • Confirm subordination percentages align with precedent transactions and rating agency expectations

4. Build the cash flow waterfall

   • Map interest waterfall: servicing fee → trustee/admin fees → senior interest → mezzanine interest (by seniority) → reserve account replenishment → excess spread to equity (or turbo principal)
   • Map principal waterfall: sequential (senior first) until triggers are met, then potentially pro rata; define trigger reversion mechanics
   • Model OC and IC trigger tests at each payment date — specify consequences of trigger breach (diversion of cash flow, trapping excess spread, acceleration of senior principal)

5. Size credit enhancement

   • Overcollateralization: target and floor OC as percentage of pool balance
   • Reserve account: initial deposit (typically 0.5%–2.0% of initial pool), floor amount, release conditions
   • Excess spread: compute available excess spread under base and stress; determine if spread capture or turbo principal is needed
   • Validate total credit enhancement (subordination + OC + reserve + excess spread) against rating agency required levels

6. Run scenario analysis

   • Execute cash flow model under base, upside, and multiple downside scenarios
   • Track key outputs per tranche: WAL, yield, principal window, break-even default rate, loss coverage ratio
   • Identify the scenario at which each tranche experiences a principal shortfall (break-even analysis)
   • Sensitivity analysis on key variables: default timing (front-loaded vs. back-loaded), recovery rate, prepayment speed

7. Document the structure

   • Produce a structural summary with tranche table, waterfall diagram, and credit enhancement summary
   • Highlight structural risks: concentration risk, commingling risk, servicer disruption, basis risk (fixed/floating mismatch)
   • Note any deviations from market-standard terms and rationale

Output

• Tranche table: For each tranche — class name, rating, initial balance, percentage of deal, coupon type/rate, expected WAL, subordination level, payment window
• Waterfall diagram: Visual or tabular representation of interest and principal payment priority, trigger tests, and cash flow redirection logic
• Credit enhancement summary: Breakdown of total CE by component (subordination, OC, reserve, excess spread) with comparison to rating agency required levels
• Scenario results matrix: Tranche-level performance metrics (principal loss, WAL, yield) across base and stress scenarios
• Risk flags: Structural features that create tail risk, trigger volatility, or rating migration sensitivity
• Recommendation: Optimal structure with rationale, or comparison of 2–3 structural alternatives with trade-offs (advance rate vs. execution certainty, equity yield vs. rating stability)

Quality Checks

• Subordination levels for each tranche meet or exceed rating agency published benchmarks [VERIFY against current Moody's/S&P/Fitch/KBRA criteria for the specific asset class]
• Cash flow waterfall is internally consistent — all cash is allocated (no leakage), and priority of payments matches legal documentation intent
• OC and IC triggers are correctly modeled with breach-and-cure logic
• Stress scenarios cover both severity (high default) and timing (front-loaded loss) dimensions
• Risk retention slice (horizontal, vertical, or L-shaped) is correctly sized at minimum 5% of total issuance [VERIFY applicable jurisdiction — US Dodd-Frank vs. EU/UK rules]
• Excess spread calculations account for servicing fees, swap costs, and trustee fees before measuring available CE
• Break-even analysis confirms each rated tranche survives its corresponding rating stress with zero principal loss
• All collateral pool statistics reconcile to the actual tape (no stale or placeholder data)