Rebalancing — calendar vs threshold methodology

Rebalancing — selling some of the asset class that grew and adding to the one that lagged — is the discipline that maintains your target asset allocation. The methodology you choose for triggering rebalances affects both expected returns and tax efficiency. Two main approaches dominate the literature: calendar-based and threshold-based.

Calendar rebalancing

Pick a fixed date — typically once a year — and rebalance on that date regardless of how much the portfolio has drifted. Common choices: end-March (FY-end), 1 January (CY-start), birthday, or any anchor date.

Pros: simple, predictable, easy to budget tax implications, easy to remember to do.

Cons: may trigger small unnecessary rebalances (drift of 1-2% generally not worth taxable events); may miss large drift between calendar dates.

Threshold rebalancing

Rebalance whenever any asset class drifts by more than a threshold percentage from target — typically 5 percentage points. So a 60% equity target rebalances back when equity hits 55% or 65%.

Pros: captures larger market moves better; tends to "sell high, buy low" more aggressively because triggers fire after meaningful moves.

Cons: requires more frequent portfolio checking; more taxable events; needs explicit thresholds set for each asset class.

The hybrid approach

Many practitioners use a combination:

• Annual calendar review.
• Plus: rebalance immediately if any asset class drifts > 7-10% off target during the year.

This captures the simplicity of calendar with the responsiveness of threshold. Outside the calendar date, you only act on big moves.

The empirical evidence

Vanguard and other research-shops have published studies comparing methods. Findings (slightly varying by study):

• Calendar (annual): adds 0.0-0.5% per year in long-run return vs no rebalancing, with controlled risk.
• Threshold (5%): adds 0.0-0.5% per year, similar.
• Combined: slightly better than either alone in turbulent markets.
• The biggest gain from rebalancing is risk control, not return enhancement. Without rebalancing, portfolios drift toward more equity over time and become riskier than the investor intended.

Tax cost of rebalancing

Each rebalance generates taxable events:

• Equity LTCG at 12.5% on equity sold.
• Equity STCG at 20% on equity sold within 12 months.
• Debt fund gain at slab rate (post-April-2023 units).
• Stamp duty (0.005%) and STT (0.001%) on equity transactions.

For a ₹10 lakh rebalance with mostly long-term equity units, the tax cost is roughly ₹1-1.5 lakh assuming the gain on sold portion is ~50%. Material enough to factor in.

Tax-efficient rebalancing methods

Use fresh contributions

If you're under-allocated to debt and over-allocated to equity, redirect new monthly SIPs toward debt funds. No selling, no taxable events. Best for smaller drifts.

Use the LTCG exemption

Realise equity gains up to ₹1.25 lakh per FY tax-free. If the rebalance requires selling ₹3 lakh of long-held equity with say ₹1.5 lakh of gain, use the annual exemption to bring the taxable portion down to ₹25k.

Tax-loss harvest first

If you have unrealised losses elsewhere, realise them in the same FY as the rebalance gain. The set-off reduces the net taxable amount.

Dynamic Asset Allocation funds

Balanced Advantage / Dynamic Asset Allocation funds rebalance internally without tax consequences for the investor. Holding more of your equity exposure through such funds reduces personal rebalancing burden — at the cost of less granular control.

Rebalancing across multiple portfolios

If you have a retirement portfolio, kids' education portfolio, and home down payment portfolio, each has its own target allocation. Rebalance each separately. Don't pool the "asset allocation" across goals — different time horizons need different allocations.

Skipping the rebalance

There are valid reasons to skip a calendar rebalance:

• Asset classes are within 2-3% of target — not worth taxable events.
• Tax cost of the rebalance > expected return improvement.
• You're using monthly SIPs to gradually rebalance over the next 6-12 months — fresh contributions can close the gap.

Don't rebalance on autopilot when the math says wait.

Rebalancing in retirement

For retirees on bucket-strategy withdrawals, "rebalancing" looks different. The annual refill from Bucket 3 to Bucket 2 (only in positive equity years) is effectively the rebalancing trigger. Outside this, no active rebalancing is typically needed — the bucket structure absorbs drift naturally.

When to deviate from any methodology

Catastrophic market events (50%+ drawdowns in any asset) often warrant immediate rebalancing regardless of date or threshold. Buying equity after a 50% crash and selling some debt at the crisis-low equity prices is one of the highest-conviction wealth-creating actions. The rebalancing rule should not prevent action when the opportunity is exceptional.