Debt funds explained: duration risk and credit risk are not the same thing

Debt funds are widely described as “the safe option”, which is how people end up surprised by them. They are not a single product and they do not carry a single risk. SEBI defines sixteen debt categories, and they differ along two independent axes that have nothing to do with each other.

Understanding those two axes is the whole subject.

Axis one: duration risk

A bond’s price moves opposite to interest rates, and how violently it moves depends on how far away its cash flows are. That sensitivity is measured as Macaulay duration, and SEBI defines most debt categories directly in terms of it:

• Overnight — securities maturing in one day. Effectively no duration risk.
• Liquid — up to 91 days.
• Ultra Short — 3 to 6 months. Low Duration — 6 to 12 months.
• Short Duration — 1 to 3 years. Medium — 3 to 4 years.
• Medium to Long — 4 to 7 years. Long Duration — over 7 years.

The rule of thumb: a fund with a duration of about 5 will lose roughly 5% of its value if yields rise one percentage point, and gain roughly that if they fall. A long-duration gilt fund is not a cash substitute. It is a rate bet, and it can have a worse year than an equity fund in a rate-hiking cycle.

Axis two: credit risk

Separately, and independently, there is the question of whether the borrower pays you back.

• Gilt funds hold government securities — at least 80% — so credit risk is effectively nil. But gilts have long maturities, so gilt funds carry heavy duration risk. Safe in one sense, volatile in the other.
• Corporate Bond funds must hold at least 80% in the highest-rated (AA+ and above) corporate paper.
• Banking & PSU funds hold at least 80% in debt of banks and public sector entities.
• Credit Risk funds do the opposite by mandate: at least 65% in AA and below. They are paid extra yield for taking default risk, and that is the entire product. The name is honest; the category was renamed to make it so.

The two axes are the point. A gilt fund has zero credit risk and high duration risk. A liquid fund has near-zero duration risk and modest credit risk. A credit risk fund can have low duration and still lose money badly. “Debt fund” tells you nothing until you know where on both axes it sits.

What actually goes wrong

Two failure modes, and they look completely different.

A rate move is a mark-to-market loss that reverses if you hold long enough, provided nothing defaults. Painful, not permanent.

A default is permanent. When a holding is downgraded or misses a payment, the fund writes it down — and if the paper is illiquid, the AMC may carve it into a segregated portfolio (a side pocket): your units in the healthy part keep trading normally, and you receive separate units for the distressed part which pay out whatever is eventually recovered.

This is why side-pocketed schemes are excluded from every screen and ranking on this site. Their NAV reflects a distressed carve-out, so any return computed from it is measuring an event, not a fund.

The tax rule changed, and it changed the case entirely

For most debt funds, every gain is added to your income and taxed at your slab rate, whatever the holding period. No long-term category, no concessional rate, no indexation.

That is a genuine change in the arithmetic. A debt fund held for five years by a 30%-bracket investor is taxed the same way a fixed deposit’s interest is. The old argument for debt funds over FDs — indexation on long holdings — is gone.

What survives is real but narrower: you control the timing of the tax (nothing is taxed until you redeem, whereas FD interest is taxed as it accrues), there is no TDS on redemption, and you can exit any day without a premature-withdrawal penalty. The full picture is in how funds are taxed.

Choosing sensibly

Match the category’s duration to the time you actually have:

• Money you might need this month — overnight or liquid.
• One to three years — ultra short, low duration or short duration.
• A genuine long horizon, and a view on rates — anything longer, understanding that you have taken a position.

And read the riskometer alongside the label: it is computed by the fund house from the actual portfolio, so a “low duration” fund holding weak credit will say so. Compare within a category on the screener — never across, for the same reason categories exist at all.

Key takeaway

“Debt fund” describes sixteen categories sitting on two independent axes — duration risk and credit risk — and a fund can be extreme on one while safe on the other. Match the category’s duration to the time you actually have, read the riskometer rather than the name, and remember that a rate loss reverses while a default does not.