Investor Corner/The asset classes/Debt Concepts
2.2.7 Credit Ratings
Credit ratings are independent grades, such as AAA, AA and BBB, that estimate a borrower's likelihood of default. Lower ratings signal higher risk and typically come with higher yields to compensate.
Who assigns them and why
Rating agencies analyse a borrower's finances, industry position and repayment history, and assign a letter grade meant to summarise their assessment of default risk in a form investors can compare quickly across very different borrowers. AAA generally represents the highest level of safety, with risk increasing as the rating scale moves down through AA, A, BBB, and further.
In India, credit ratings are assigned by agencies authorised by SEBI: CRISIL, ICRA, CARE, India Ratings (Fitch group), Acuite and Brickwork. Each agency evaluates an issuer's financial health, business position, industry conditions and management quality, then assigns a rating on a scale from AAA (highest credit quality, lowest default risk) through AA, A, BBB (investment grade) down to BB, B, C and D (below investment grade, with D indicating actual default).
Ratings are opinions, not guarantees. They reflect the agency's assessment of the probability of timely debt servicing at a point in time. Rating agencies have been wrong before: several securities rated AA or above have defaulted in India, most notably in the IL&FS episode where highly rated instruments suddenly became worthless. The rating is a useful starting point for credit analysis, not the final word.
The line that matters most
The distinction between investment grade, generally BBB and above, and below investment grade is one of the more important lines on the rating scale. Many institutional investors and some mutual fund categories are restricted from holding anything below investment grade, which affects how easily a downgraded bond can be resold and can amplify price moves when a downgrade actually happens.
For debt mutual fund investors, the most critical boundary is between investment grade (BBB and above) and below investment grade (BB and below). Most mainstream debt funds limit their holdings to investment-grade securities, and SEBI's categorisation rules require certain fund types (like corporate bond funds) to hold a minimum percentage in AA+ or higher rated instruments. Funds that venture below this threshold (credit risk funds) must be clearly labelled, but the higher yield they promise comes with meaningfully higher default risk.
A rating downgrade, even within investment grade (say from AA+ to AA), causes the bond's price to fall as the credit spread widens to reflect the perceived increase in risk. For a fund holding that bond, this translates into a NAV decline. Multiple downgrades across a fund's portfolio during a credit cycle can produce sustained underperformance that looks modest on any single day but compounds into a meaningful loss over months.
Using ratings sensibly
Credit ratings are a genuinely useful starting filter, but they are not infallible, and rating agencies have been wrong before, sometimes significantly so during periods of financial stress. Ratings are best treated as one input into a credit decision, combined with diversification across issuers, rather than relied upon as the sole basis for taking on credit risk.
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When evaluating a debt fund, check not just the current portfolio rating distribution (reported in the factsheet) but also the trend. A fund that has been gradually shifting from AAA to AA to A rated paper is reaching for yield by accepting incrementally more credit risk. This strategy works fine in benign credit environments but can produce sharp losses when the cycle turns. Conservative investors should prefer funds with a stable or improving credit quality profile over those that chase yield through rating migration.