Corporate Bond Fund: What the AA+ and Above Rule Means for Your Debt Money

A corporate bond fund is the debt fund for people who want a bit more yield than a government-securities fund but don’t want to chase it through lower-rated paper. The whole category hangs on one rule from SEBI: at least 80% of the money has to sit in corporate bonds rated AA+ or above. Everything else about how these funds behave, good and bad, follows from that line.

We’ll go through what the rule actually says, how the 10% liquidity buffer changes the arithmetic, what a fund manager is still free to do, and where the risk hides in a category that sounds very safe on paper.

What SEBI’s definition of a corporate bond fund says

SEBI’s Master Circular for Mutual Funds dated March 20, 2026 lists 17 debt scheme categories. Corporate Bond Fund is number 11. Its scheme characteristic is short: a minimum investment in corporate bonds of 80% of total assets, and only in AA+ and above rated corporate bonds. The uniform description a fund house has to use is “an open ended debt scheme predominantly investing in AA+ and above rated corporate bonds”.

That’s it. Notice what is missing. Unlike the ultra short, short, medium and long duration categories, the corporate bond fund row says nothing about Macaulay duration. A corporate bond fund can hold one-year paper or ten-year paper. The category tells you about credit quality, not about how much the fund will move when interest rates change.

The same circular came alongside a bigger change. It was updated in line with the SEBI (Mutual Funds) Regulations, 2026, which came into force from April 1, 2026. The category rules themselves carry over in the same table format investors have seen for years.

How it sits next to its neighbours

The easiest way to understand a corporate bond fund is to put it beside the two categories people confuse it with. All three figures below come from the same SEBI table.

So a corporate bond fund and a credit risk fund are almost mirror images. One is forced to the top of the rating ladder, the other is forced below AA+. A banking and PSU fund is defined by who issued the paper rather than by the rating, which is why the two can end up owning a lot of the same names.

The 10% liquid assets rule and why 80% is really 72%

Here’s the detail most explainers skip. Paragraph 5.7 of the master circular says all open-ended debt schemes, except overnight, liquid, gilt and 10-year constant maturity gilt funds, must hold at least 10% of net assets in liquid assets. Liquid assets, as defined in paragraph 5.6.1, include cash and government securities, among other things.

Those liquid assets are not counted when SEBI checks the category’s asset allocation. For four categories, corporate bond funds included, the base for the allocation limit is net assets minus that minimum 10%. SEBI’s own illustration uses the banking and PSU fund: 80% of 90% of net assets, which works out to a 72% minimum. The corporate bond fund has the same 80% figure and is named in the same clause, so the same arithmetic applies to it.

The rating rule tells you what the fund can’t buy. It tells you nothing about how long the money is locked into those bonds, and that is where most of the price movement comes from.

Worked example: a ₹1,000 crore fund

Take a hypothetical corporate bond fund with net assets of ₹1,000 crore. These are illustrative numbers, not any real scheme.

• Minimum liquid assets at 10%: ₹100 crore.
• Base for the allocation test: ₹1,000 crore minus ₹100 crore, which is ₹900 crore.
• Minimum in AA+ and above corporate bonds: 80% of ₹900 crore, which is ₹720 crore.
• Room left over: ₹1,000 crore minus ₹100 crore minus ₹720 crore, which is ₹180 crore.

That ₹180 crore is where portfolios differ. What can go in there depends on the scheme information document of each fund. One fund may keep it in government securities and money market paper. Another may use it more actively. The master circular does allow debt category schemes to put residual money into InvITs, within separate ceilings, and it lists the categories that can’t: overnight, liquid, ultra-short term, ultra short to short term and money market funds. Corporate bond funds aren’t on that excluded list.

So when you compare two corporate bond funds, the 72% core will look alike. The other 28% is where you’ll find the differences.

How much can one company take up

A fund that buys only top-rated paper can still be concentrated. SEBI caps that through a single-issuer limit for actively managed debt schemes other than credit risk funds. The master circular sets it at 10% of NAV in debt and money market securities rated AAA, and 8% of NAV in those rated AA, with an overall single-issuer limit of 10% of NAV.

In our ₹1,000 crore example, that means no more than ₹100 crore in one AAA issuer. The limit doesn’t apply to government securities, treasury bills or triparty repo on them. That’s why you’ll often see the largest single line in a corporate bond fund portfolio being a government bond rather than a company.

Practically, a fund with ₹720 crore of AA+ and above paper and a ₹100 crore cap per AAA issuer needs at least eight different issuers just to fill the core. Most funds hold far more, but the cap gives you a floor on diversification.

Where a corporate bond fund’s returns come from

Two engines. The first is accrual: the interest the bonds pay. The second is mark-to-market: bond prices go up when yields fall and down when yields rise. Over a short holding period, the second can overwhelm the first.

Worked example: the accrual side

Suppose a fund’s portfolio yield to maturity is 7.2% and its expense ratio is 0.4%. Again, these are made-up numbers. If yields stay flat for a year and nothing defaults, the investor’s return should land roughly around 7.2% minus 0.4%, so about 6.8%. That gap between portfolio yield and expense ratio is the closest thing a debt fund has to a “default” return.

Worked example: the rate-move side

Now say the same fund has a modified duration of 3 years and market yields on its bonds rise by 0.50 percentage point. Using the standard approximation (change in price is roughly minus modified duration times change in yield), the portfolio’s value falls by about 3 times 0.50%, which is 1.5%. That one move wipes out more than two months of the 6.8% accrual in our example.

If yields fall by the same amount, the gain is about 1.5%. This is why two corporate bond funds with near-identical credit quality can show quite different one-year returns. Our guide to bond duration goes through the maths in more detail.

A corporate bond fund with long duration is a rate call wearing a credit-quality badge. Check the duration before you check the rating mix.

The risks that AA+ doesn’t remove

Interest rate risk. Covered above. Since SEBI doesn’t fix a duration band for this category, it’s on you to read the fund’s factsheet and see where it sits.

Rating migration. A bond that is AA+ today can be downgraded. When that happens, its price usually drops before anyone can sell, and the fund’s AA+ share can slip. The fund then has to work its way back to the category rule.

Liquidity during stress. Corporate bonds don’t trade like Nifty stocks. That’s part of why SEBI wants the 10% liquid buffer. The circular also brings open-ended debt schemes, apart from overnight and gilt funds, under a swing pricing framework for net outflows, with a mandatory full swing during market dislocation for high-risk schemes. In plain words: when lots of investors rush for the exit in a crisis, the people leaving can be made to bear more of the cost of selling.

Concentration in one sector. Open the portfolio and add up how much sits with lenders: banks, NBFCs and PSU financiers. If that’s most of the fund, a stress event in one sector hits a large part of the portfolio at once, whatever the ratings say.

How we’d read a corporate bond fund factsheet

When we look at one of these funds, we go in this order:

1. Modified or Macaulay duration. This tells you how much the fund will move for a given rate change. It’s the number that drives short-term returns.
2. Yield to maturity versus expense ratio. The difference is your rough accrual return if rates and ratings hold still.
3. Rating break-up. AAA, AA+, sovereign, cash. Watch how much of the 28% outside the core is in sovereign paper versus anything else.
4. Top issuers. How close is the largest corporate issuer to the 10% cap? A fund running near the limit across several names is more concentrated than its rating mix suggests.
5. Riskometer. It gives the fund house’s own summary of how risky the scheme is, and SEBI’s duration and issuer calculations use the full net assets as the base.

Who a corporate bond fund suits

It fits someone with a two to three year view on money they don’t want in equities, who is fine with small mark-to-market swings and wants better credit quality than a credit risk fund offers. It doesn’t suit money you need next month. A liquid or overnight fund is built for that.

It also isn’t a fixed deposit. There’s no guaranteed return, the NAV moves daily, and the fund can fall in a quarter when yields jump. If that’s uncomfortable, start by matching the fund’s duration to your holding period. A fund with a duration close to the number of years you plan to stay invested has a better chance of the accrual making up for any rate moves along the way. For a broader view of sizing and limiting risk across your money, see our guide to risk management.

Quick recap

A corporate bond fund must put at least 80% of its assets in AA+ and above rated corporate bonds, measured after setting aside the mandatory 10% liquid buffer, so the effective minimum is 72% of net assets. SEBI sets no duration band for it, which means rate risk varies widely across funds. Single-issuer caps of 10% of NAV for AAA paper keep concentration in check. Read duration first, yield minus expenses second, and the rating mix third.

Disclaimer: This article is for information and education only and is not investment advice. Please do your own research or consult a SEBI-registered adviser before making any investment decision.