Mark-to-market (MTM) for debt holdings in mutual funds
Mark-to-market (MTM) valuation of debt holdings is the practice of valuing a mutual fund’s fixed-income portfolio at current market prices (based on current market yields) rather than at the original purchase price or on an amortised cost basis. Under full MTM, the NAV of a debt mutual fund rises when market interest rates fall (because bond prices rise when yields fall) and falls when market interest rates rise (because bond prices fall when yields rise). This price sensitivity to interest rate movements is the primary source of NAV volatility in debt funds.
Regulatory basis
India has progressively moved debt mutual funds to full MTM valuation:
- Pre-2019: Securities with residual maturity up to 60 days could be valued on an amortisation basis (straight-line accretion from purchase price to face value at the implied yield). This smoothed short-term NAV volatility for liquid and short-duration funds.
- SEBI Circular SEBI/HO/IMD/DF4/CIR/P/2019/102 (24 September 2019): Mandated full MTM valuation for all debt and money-market securities with residual maturity above 30 days, effective 1 April 2020. Securities with residual maturity up to 30 days continue to be valued on amortised cost.
- SEBI Master Circular (2024): Consolidates the MTM valuation framework.
How MTM works
When a bond’s yield in the secondary market changes, its price changes inversely. The relationship is quantified by modified duration:
Approximate price change (%) ≈ − Modified Duration × Change in yield (%)
Example:
- A debt fund holds a 10-year government security with a modified duration of 8 years.
- If market yields rise by 50 basis points (0.50%), the bond price falls by approximately 8 × 0.50 = 4%.
- The fund’s NAV falls by approximately 4% on that movement (ignoring other holdings).
Conversely, if yields fall by 50 basis points, the NAV rises by approximately 4%.
MTM therefore directly transmits interest rate volatility into the fund’s NAV on a daily basis.
Valuation agencies
SEBI has empanelled two agencies to provide daily MTM prices for debt securities:
- CRISIL Ltd (a SEBI-registered credit rating agency that also operates a debt valuation service).
- ICRA Analytics (a subsidiary of ICRA).
Each agency publishes prices by approximately 7 p.m. on each business day for thousands of debt instruments: government securities, state development loans, corporate bonds, commercial paper, certificates of deposit, and treasury bills. AMCs use these agency prices as the primary source for computing daily NAV of debt schemes. Full methodology is in the NAV computation article.
Impact on debt fund categories
The MTM impact varies significantly by scheme category:
| Scheme category | Typical modified duration | MTM sensitivity |
|---|---|---|
| Overnight fund | Near 0 | Negligible |
| Liquid fund | 30–91 days (amortised for sub-30d) | Very low |
| Ultra-short duration | 3–6 months | Low |
| Short duration | 1–3 years | Moderate |
| Medium duration | 3–4 years | Moderate to high |
| Long duration | 7+ years | High |
| Gilt fund (long-term) | 10–20 years | Very high |
Long-duration gilt funds can see NAV swings of 5%–10% or more in a single quarter during periods of significant interest rate change, making them volatile instruments despite investing only in sovereign (risk-free for credit purposes) securities.
MTM for credit events
Beyond interest rate risk, MTM also captures credit events (rating downgrades or defaults). When a security held by a debt fund is downgraded, its market price falls (because buyers demand a higher yield to compensate for perceived higher credit risk). The MTM valuation of the security falls, which reduces the fund’s NAV.
In extreme cases (defaults), the SEBI-empanelled valuation agencies set the price near zero or at estimated recovery value. This produces a sharp one-day NAV drop. The side-pocketing mechanism addresses how such events are managed to prevent investor panic and cascading redemptions.
Comparison with amortisation
| Feature | Amortisation (up to 30 days) | Full MTM (above 30 days) |
|---|---|---|
| NAV behaviour | Smooth, incremental daily accretion | Fluctuates with market yields |
| Investor experience | Predictable, bank-FD-like appearance | Volatile, equity-fund-like in some categories |
| Risk transparency | Low (hides interest rate risk) | High (reflects actual market risk daily) |
| Arbitrage opportunity | Higher (old regime allowed NAV arbitrage) | Lower |
Related articles
- Daily MTM for debt mutual funds
- NAV computation methodology
- Side-pocketed scheme
- Illiquid asset workout
- Riskometer
- SEBI (Mutual Funds) Regulations 1996
References
- SEBI Circular SEBI/HO/IMD/DF4/CIR/P/2019/102 (24 September 2019), MTM valuation mandate.
- SEBI Master Circular for Mutual Funds (2024).
- AMFI Best Practices Guidelines on valuation.
- CRISIL and ICRA Analytics debt valuation methodologies.