Rebalancing: Why and How Often

Suppose you decide that 60% of a ₹10 lakh portfolio should be in equity and 40% in debt. A year later equities have risen 25% and debt has earned 7%. Without a single trade, your equity is now worth ₹7.5 lakh and your debt ₹4.28 lakh. The portfolio is about 64% equity and 36% debt. Another strong year or two and it could be close to 70:30 — a noticeably riskier portfolio than the one you chose.

Rebalancing is the process of bringing a portfolio back to its intended mix. The SEC's investor-education glossary describes it as returning a portfolio to its original asset allocation, which becomes necessary because over time some investments grow faster than others and holdings drift out of line with your goals.

Why drift is a risk, not a reward

It is tempting to see drift as good news: equity grew, so let it run. The problem is what drift does to risk. An unrebalanced portfolio gradually concentrates in whatever has performed best recently. After a long equity rally, it holds more equity than you planned at exactly the point where the gains are largest and a reversal would hurt most. The allocation you chose because it matched your time horizon and your tolerance for losses no longer exists.

The reverse happens after a fall. If equities drop sharply, a 60:40 portfolio might become 50:50, more conservative than intended — and if you never restore the balance, you participate less in any later recovery than your plan assumed.

The built-in discipline

Rebalancing mechanically trims whatever has grown beyond its target and adds to whatever has fallen behind. In effect, it sells some of what has gone up and buys some of what has gone down, without any forecast about what happens next. This runs against instinct. After a rally, selling winners feels like giving up on a good thing; after a fall, buying more of the loser feels reckless. Having a rule decided in advance takes the emotion out of the decision.

It is important to be clear about what rebalancing is not. It is not a market-timing strategy and doesn't promise higher returns. In a long, steady bull market, a portfolio that is never rebalanced and ends up mostly in equity may well finish with more money than a disciplined 60:40 one. The purpose of rebalancing is to keep risk where you decided it should be.

Two common approaches

• Calendar rebalancing: review the portfolio at a fixed interval — once a year is common, sometimes every six months — and restore the target mix regardless of how far it has drifted.
• Threshold (or band) rebalancing: act only when an asset class moves more than a set distance from its target, for example 5 percentage points either way. A 60% equity target would trigger rebalancing below 55% or above 65%.

Calendar rebalancing is simple and easy to remember — some people tie it to a date like their birthday or the start of the financial year. Threshold rebalancing responds to actual market moves, so it may trade less in calm years and more in volatile ones. Many investors combine the two: check once or twice a year, but only act if the drift exceeds the band.

Whichever you choose, avoid rebalancing too often. Checking every week and trading on small deviations adds costs and taxes without meaningfully changing your risk, and it keeps your attention on short-term price moves — the very thing a rules-based approach is meant to quiet. The band should be wide enough that ordinary market noise doesn't trigger it, and narrow enough that a genuine drift doesn't go unnoticed for years.

Ways to rebalance with less friction

Selling has costs. In India, redeeming mutual fund units or selling shares can trigger capital gains tax, and some funds charge an exit load if units are redeemed within a set period. Frequent trading also adds transaction costs. The rules on taxes and loads change and differ by product, so check the current position for what you hold. A few techniques reduce the need to sell:

• Redirect new money. If equity is overweight, point new SIP instalments or lump sums toward the underweight asset until the mix is back on target.
• Use cash flows. Dividends, interest or maturing deposits can be reinvested in the underweight asset.
• Withdraw from the overweight asset. If you need to take money out, take it from whatever has grown beyond its target.
• Rebalance within tax-advantaged or long-term schemes first, where switching may have fewer consequences, if that applies to your holdings.

Rebalancing and changing your target are different things

Rebalancing restores the mix you chose. Changing the mix itself is a separate decision that should be driven by changes in your life — a shorter time horizon as a goal approaches, a new dependant, a change in income — rather than by recent market performance. Mixing the two up is how people end up raising their equity target after a rally and cutting it after a crash, which is the opposite of what rebalancing is meant to achieve.

Some products do the rebalancing for you. Balanced advantage and multi-asset funds adjust their mix within the limits set in their scheme documents, and lifecycle funds abroad shift toward debt as their target year approaches. These can be convenient, but it is still worth knowing what rules the fund follows and how it fits with the rest of what you own.

A simple annual routine

• Add up the current value of each asset class across all your accounts and funds.
• Compare each with its target percentage.
• If anything is outside your band, decide how to move it back — new money first, then switches or sales.
• Note any tax or exit-load consequences before you sell.
• Write down what you did and why, so next year's review starts from a record rather than memory.

Rebalancing is unglamorous: an hour or two once a year, a few transactions, a spreadsheet. But it is one of the few investing habits that reliably does what it says — keeping the risk you are taking matched to the risk you meant to take.