Note: This is an evergreen explainer. It contains no current market data and no view on where interest rates are heading.
Debt funds are often described as the steady part of a portfolio, and over long periods many are. But their returns do respond to interest-rate cycles — sometimes sharply — and the response depends on a few measurable features of each fund. Understanding them makes debt-fund returns far less surprising.
Where debt fund returns come from
Accrual is the interest the fund's bonds and money-market instruments pay. The portfolio's yield to maturity, shown in the factsheet, is a starting indicator of accrual before expenses.
Mark-to-market is the daily revaluation of holdings at current prices. When market yields change, bond prices change, and so does the fund's NAV — by an amount that depends on the fund's modified duration.
Over short periods, mark-to-market moves can dominate. Over long periods, accrual tends to do most of the work.
How policy decisions reach bond yields
The RBI's Monetary Policy Committee sets the policy repo rate. By law it must meet at least four times a year; in practice it has usually met six times. Its framework targets CPI inflation of 4% within a band of 2% to 6%, a target the government retained for April 2026 to March 2031.
A change in the policy rate passes quickly to overnight and very short-term rates. Longer-term yields respond more loosely: they reflect expectations of future policy, inflation, government borrowing, banking-system liquidity and global rates. Markets often move before a decision, on expectations, so the announcement itself can produce little change.
A stylised cycle
| Phase | Yields | Longer-duration funds | Shorter-duration funds |
|---|---|---|---|
| Rates rising | Rise | Price falls offset accrual; returns can be weak or negative for a time | Small price impact; accrual improves as holdings roll over |
| Rates high and stable | High, steady | Strong accrual; little price movement | Strong accrual |
| Rates falling | Fall | Price gains add to accrual | Modest gains; accrual gradually declines |
| Rates low and stable | Low, steady | Lower accrual; exposed to the next rise | Lower accrual |
Real cycles are messier. Yields at different maturities do not always move together — the yield curve can steepen or flatten — and phases do not arrive on a timetable.
Duration is the dial
Debt fund categories differ mainly in how much interest-rate risk they take, from overnight and liquid funds (very short) through money-market, low and short duration, to medium, long duration, dynamic bond and gilt funds (which can be long). A useful approximation:
Price change ≈ − modified duration × change in yield
For illustration, a fund with a modified duration of 6 would see a price effect of roughly −3% if yields across its holdings rose by half a percentage point — offset over time by accrual at the now-higher yields. A fund with a duration of 0.5 would barely move. The Bond Yield & Cashflow tool shows the mechanics on a single bond, and why bond prices fall when rates rise explains the maths.
Credit spreads through the cycle
Corporate bonds yield more than government securities of similar maturity. That gap — the credit spread — tends to widen when the economy slows or stress rises, as investors demand more for taking credit risk, and to narrow in calmer times. Funds holding lower-rated papers are more exposed to these swings, and to the occasional sharp fall when an issuer is downgraded or defaults. Credit ratings explained covers how to read the ratings involved.
Target maturity funds
Some debt funds and ETFs hold bonds until a defined maturity date. If you hold until that date, interim mark-to-market moves fade, and your return tends to approximate the yield at which you invested, less costs — subject to credit events and to how coupons are reinvested. For a goal with a fixed date, this makes outcomes easier to anticipate.
What this means for you
- Choose duration by horizon, not by forecast. Money needed within a year sits more comfortably in very low-duration funds; a horizon of several years can tolerate more duration in exchange for interim swings.
- Read past returns in context. A long-duration fund's strong year often reflects a falling-rate phase, not something that repeats on demand.
- Check the factsheet. Modified duration, YTM, credit quality and the Potential Risk Class tell you most of what you need — see how to read a riskometer.
- Remember tax. Gains on debt fund units bought from April 2023 are taxed at your slab rate — see how investments are taxed.
Explore debt categories on the debt funds page, or compare with deposits using the FD Calculator.