A rating of an investment vehicle is useful, but it is not the whole case. Before making a decision, investors need to review the collateral, the underwriting, the protection layers, the payment waterfall, and the reporting and servicing setup that keep a transaction working after closing the investment.
Rating- A Starting Point
A rating is usually built from several layers, not one single opinion. Its a framework which is split into master criteria, cross-sector criteria, sector-specific criteria, and tailored criteria. Rating agencies look at both the broad rules of structured finance and the details of the asset class in front of them.
In its Canada RMBS guidance, Fitch makes this very practical. It starts with borrower equity, loan-to-value, credit score, debt service, occupancy, property type and loan purpose, then moves to loss severity, cash-flow stresses, servicing assumptions, and data adequacy. That order is useful for investors too: first ask what can go wrong in the pool, then ask whether the structure can absorb it.
The Five Checks
Asset quality. Start with what sits in the pool. In RMBS, that usually means LTV, insured vs. uninsured loans, owner-occupied vs. investor loans, province mix, seasoning, and delinquency status. Fitch’s Canada RMBS criteria puts borrower equity and sustainable LTV at the center of default analysis, and it also adjusts for geographic concentration and refinance risk. For auto ABS, the practical equivalents are borrower score bands, new vs. used cars, original term, and recovery history. For credit cards, look at payment rate, charge-offs, and how much of the book revolves rather than pays in full. For CMBS, focus on property cash flow, tenant mix, lease rollover, and refinance exposure at maturity.
Borrower and obligor behaviour. A strong pool is not just about today’s collateral values. It is also about who is likely to keep paying under stress. Fitch’s Canada RMBS factors include credit score, TDSR, occupancy, property type, loan purpose, current delinquency status, and seasoning-related behaviour. In simple terms, higher leverage and weaker payment capacity usually mean higher default risk, while owner-occupied and better-scored borrowers tend to perform better. In other asset classes, the same question applies differently: in auto ABS, watch payment history and first-pay defaults; in credit cards, watch payment rate, utilization, and charge-off trends; in CMBS, watch tenant rollover, DSCR, and sponsor quality.
Loss protection. This is where investors ask, “How much bad performance can the structure absorb before my class gets hit?” The common tools are subordination, excess spread, reserve funds, insurance, and overcollateralization. A simple example: if a deal has 8% subordination, 2% reserve, and 1% excess spread, senior notes effectively start with about 11% of first-loss support. Another example: if a pool has $105 of assets backing $100 of notes, that is 5% overcollateralization. Fitch’s Canada RMBS criteria also shows why this matters: losses can rise not just from defaults, but from lower property values, quick-sale discounts, longer liquidation timelines, and carrying costs. That is why investors should never look at credit enhancement in isolation.
Cash-flow structure and waterfall. Even a good pool can fail in a bad structure. Fitch says its cash-flow analysis tests whether collateral collections are enough to pay principal and interest on the rated obligations, based on transaction terms. It explicitly considers prepayments, servicing fees, default timing, and negative spread on reinvestments. For investors, the practical check is simple: who gets paid first, what triggers switch the deal into protection mode, and how much liquidity is available if collections arrive late?
Reporting, servicing, and data quality. This is the most underrated check. Fitch’s Canada RMBS criteria asks for loan-level data at issuance and on a quarterly basis, including LTV, credit score, TDSR, arrears/default history, prepayment information, and vintage performance. It also says weak or missing data can lead to conservative assumptions or even a rating cap. In practice, investors should ask for a clean loan tape, consistent vintage reporting, servicer performance history, remediation language for data exceptions, and a clear process if representations are breached. A strong structure still needs good reporting to stay trusted after pricing.
A Quick Cross-Asset Snapshot
| Check | RMBS | Auto ABS | CMBS |
|---|---|---|---|
| Asset quality | LTV, insurance, province mix | New/used mix, term, vehicle type | DSCR, occupancy, property type |
| Borrower behaviour | Credit score, TDSR, occupancy, seasoning | Score bands, payment history | Tenant rollover |
| Loss protection | Subordination, reserve, insurance | Subordination, excess spread, reserve | Subordination, interest reserve |
| Cash flow | Sequential pay, triggers, liquidity | Amortization triggers, collection timing | Payment priority, appraisal triggers |
| Reporting and servicing | Loan tape, vintages, arrears data | Recoveries, repossession metrics | Rent roll, lease expiry |
That table is not a rating model. It is a due-diligence shortcut. Across asset classes, the same five checks still matter, even if the metrics change.
How the Waterfall Usually Work
Collections –>> Senior Notes Interest –>> Senior Notes Principal –>> Junio Notes Interest and Principal –>> Replenish Reserves
In live deals, waterfalls can be more detailed than this. But if you cannot explain the payment order in one minute, you probably should not rely on the rating alone.
A rating could be a starting point to understand the investment instrument, not a substitute for judgment. If investors check asset quality, borrower behavior, loss protection, cash-flow mechanics, and reporting discipline before making any opinion, which then can be used to ask better questions for understanding the overall structure.
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