What is Portfolio Rebalancing?
Portfolio rebalancing is the process of realigning the weightings of the assets in your portfolio to match your original target allocation. Over time, as different investments grow at different rates, your portfolio naturally drifts away from its intended mix. Rebalancing brings it back.
Suppose you build a portfolio with 70% stocks and 30% bonds. After a strong year in the stock market, your portfolio might shift to 80% stocks and 20% bonds. You now carry more risk than you planned for. Rebalancing means selling some stocks and buying bonds to restore the 70/30 split.
Portfolio Drift: Before vs After Rebalancing
Why Rebalancing Matters
Without rebalancing, a portfolio's risk profile changes over time. A conservative investor who never rebalances could end up with an aggressive portfolio after a bull market, leaving them overexposed right before a downturn. Rebalancing enforces discipline and keeps your risk level consistent with your goals.
- Risk control: Prevents your portfolio from becoming riskier (or more conservative) than intended
- Disciplined investing: Forces a systematic buy-low, sell-high behaviour
- Goal alignment: Keeps your asset mix matched to your time horizon and risk tolerance
- Reduced emotional decisions: A rebalancing rule removes the temptation to chase hot sectors
Rebalancing is About Risk, Not Returns
The primary purpose of rebalancing is to control risk, not to maximise returns. By selling assets that have grown beyond their target and buying those that have lagged, you maintain the risk level you originally chose. Any return benefit is a secondary effect of disciplined allocation management.
When Should You Rebalance?
There are three main approaches to timing your rebalancing, each with its own trade-offs between simplicity, effectiveness, and transaction costs.
Calendar Rebalancing
The simplest method: rebalance on a fixed schedule, such as quarterly, semi-annually, or annually. You pick a date (or dates) and realign your portfolio regardless of how much it has drifted. Annual or semi-annual rebalancing is the most common choice and works well for the majority of investors.
Threshold Rebalancing
Instead of using a calendar, you set tolerance bands around each target allocation. You only rebalance when an asset class drifts beyond its band. For example, if your target for stocks is 60%, you might set a 5% threshold and only rebalance when stocks move above 65% or below 55%.
Hybrid Approach
Many advisors recommend combining both methods: check your portfolio on a set schedule (e.g., quarterly), but only trade if drift exceeds your threshold. This approach avoids unnecessary trades while ensuring you never go too long without reviewing your allocation.
Calendar Rebalancing
- Simple and easy to follow
- Set-it-and-forget-it schedule
- May trade when drift is minimal
- Could miss large mid-year swings
- Best for: hands-off investors
Threshold / Hybrid
- Only trades when drift is material
- Responds to market events faster
- Lower transaction costs over time
- Requires monitoring (or automation)
- Best for: cost-conscious investors
The 5/25 Rule
A widely cited guideline: rebalance when any asset class drifts by 5 percentage points in absolute terms, or 25% of its target weight in relative terms (whichever is smaller). For a 20% target, the relative trigger would be 5% (25% of 20%), so you would act at 15% or 25%.
Rebalancing Strategies
Once you decide when to rebalance, you need to decide how. The method you choose affects transaction costs, taxes, and the effort required.
1. Sell High, Buy Low (Traditional)
The classic method: sell overweight assets and use the proceeds to buy underweight ones. This is the most direct approach and immediately restores your target allocation. However, selling in a taxable account triggers capital gains, which is the primary drawback.
2. Cash Flow Rebalancing
Instead of selling winners, direct new contributions (salary deposits, dividends, interest payments) toward underweight asset classes. Over time, this brings the portfolio back into balance without selling anything. It is the most tax-efficient method, but works slowly and may not be sufficient during large market moves.
Dividend Reinvestment as a Rebalancing Tool
If your investments pay dividends, you can direct those dividends toward underweight asset classes rather than reinvesting them in the same fund. This is a zero-cost way to nudge your allocation back toward its target between formal rebalancing events.
3. Band (Tolerance) Rebalancing
Set upper and lower bands around each target allocation. When an asset drifts outside its band, rebalance only that asset back to the target -- not the entire portfolio. This minimises trades and keeps costs low while still controlling drift on the assets that matter most.
4. Percentage-of-Portfolio Rebalancing
Rather than restoring exact targets, you bring each asset partially back toward its target. For example, if stocks have drifted to 75% against a 70% target, you might sell only enough to bring them down to 72%. This reduces transaction costs and taxes at the expense of slightly looser allocation control.
| Strategy | Tax Efficiency | Speed | Effort | Best For |
|---|---|---|---|---|
| Sell High, Buy Low | Low | Immediate | Medium | Tax-advantaged accounts |
| Cash Flow | High | Slow | Low | Accumulation phase |
| Band / Tolerance | Medium | Medium | Medium | Cost-conscious investors |
| Partial Rebalance | Medium | Medium | Low | Large taxable portfolios |
Tax Implications of Rebalancing
In a taxable brokerage account, selling appreciated assets to rebalance creates capital gains, which means a tax bill. Understanding the tax consequences and planning around them can save you a significant amount over your investing lifetime.
Short-Term vs Long-Term Capital Gains
Assets held for more than one year qualify for the lower long-term capital gains rate in most jurisdictions. If you must sell to rebalance, prefer selling lots held longer than 12 months. Better yet, use specific lot identification (such as FIFO, LIFO, or highest-cost-first) to minimise the gain on each sale.
Beware the Wash-Sale Rule
If you sell a position at a loss and repurchase a "substantially identical" security within 30 days before or after, the loss is disallowed for tax purposes. When rebalancing and tax-loss harvesting simultaneously, ensure you do not trigger a wash sale by buying back the same fund too quickly.
Tax-Advantaged Accounts First
The simplest way to avoid tax complications is to do your rebalancing inside tax-advantaged accounts such as IRAs, 401(k)s, ISAs (UK), or SIPPs. Trades inside these accounts have no immediate tax consequences. If your portfolio spans both taxable and tax-advantaged accounts, prioritise rebalancing trades in the tax-sheltered ones.
Tax-Loss Harvesting While Rebalancing
Rebalancing creates an opportunity: if any asset class is both overweight and trading at a loss, you can sell it to simultaneously rebalance and harvest a tax loss. The harvested loss offsets gains elsewhere in your portfolio. Replace the sold fund with a similar (but not substantially identical) fund to maintain your target allocation without triggering the wash-sale rule.
Track Your Cost Basis
Accurate cost basis records are essential for tax-efficient rebalancing. AllInvestView tracks your cost basis across all holdings automatically, so you always know the tax impact of a rebalancing trade before you execute it. Learn more in our capital gains tax guide.
How to Rebalance Step by Step
Follow these four steps each time you rebalance. The process takes just a few minutes once you have your data ready.
Step 1: Assess Your Current Allocation
Log in to your portfolio tracker and review the current percentage weight of each asset class. Note any asset classes that have drifted significantly from their targets. If you use AllInvestView, the dashboard shows your allocation breakdown in real time across all connected accounts.
Step 2: Determine Your Target Allocation
Confirm that your original target still reflects your goals, time horizon, and risk tolerance. Life changes -- a new job, approaching retirement, a major expense -- may warrant adjusting the target itself before rebalancing back to it. If your target needs updating, set the new targets first, then rebalance to the new mix.
Step 3: Calculate the Trades Needed
For each asset class, calculate the difference between its current value and its target value. This tells you how much to sell or buy.
| Asset Class | Target | Current | Drift | Action |
|---|---|---|---|---|
| US Stocks | 60% | 68% | +8% | Sell $4,000 |
| Int'l Stocks | 15% | 12% | -3% | Buy $1,500 |
| Bonds | 20% | 16% | -4% | Buy $2,000 |
| REITs | 5% | 4% | -1% | Buy $500 |
Step 4: Execute and Verify
Place your trades, starting with sales (to generate the cash for purchases). After all trades settle, verify that your allocation is back within your target bands. Document the rebalancing event and set a reminder for the next one.
Combine with New Contributions
If you are adding new money at the same time, direct it toward underweight asset classes first. This reduces the amount you need to sell, which lowers transaction costs and tax impact. Cash flow rebalancing and periodic rebalancing work best when combined.
Rebalancing Tools and Automation
Rebalancing by hand with a spreadsheet works, but modern portfolio tools make the process faster and less error-prone. The right tool calculates your drift, suggests exact trade amounts, and can even factor in tax implications.
Manual vs Automated Rebalancing
Manual (Spreadsheet)
- Full control over every trade
- No software dependency
- Time-consuming to calculate
- Prone to arithmetic errors
- No real-time data integration
Automated (Portfolio Tool)
- Instant drift calculations
- Real-time price data
- Tax-aware trade suggestions
- Multi-account aggregation
- Rebalancing history and alerts
How AllInvestView's Rebalance Tool Works
AllInvestView's built-in rebalancing tool streamlines the entire process. Here is how it works:
- Set target allocations: Define percentage targets for each asset class or individual holding within a portfolio.
- View real-time drift: The tool pulls current market prices and shows you exactly how far each position has drifted from its target, in both percentage and monetary terms.
- Get trade suggestions: With one click, the tool calculates the specific buy and sell amounts needed to restore your target allocation.
- Review and execute: Review the suggested trades, make adjustments if needed, and execute them through your broker.
Works Across All Your Accounts
If you connect your brokerage accounts via AllInvestView's broker sync feature, the rebalancing tool considers your entire portfolio across multiple brokers. This gives you a true whole-portfolio view, preventing you from rebalancing one account in isolation while ignoring drift in another.
When Automation Makes Sense
Automated rebalancing tools are most valuable when you have multiple accounts, many holdings, or complex tax situations. If you hold a simple two-fund portfolio in a single tax-advantaged account, manual rebalancing once a year is perfectly adequate. As your portfolio grows in complexity, the time savings and accuracy of a dedicated tool pay for themselves quickly.
Don't Over-Rebalance
Rebalancing too frequently -- weekly or even monthly -- generates unnecessary transaction costs and tax events without meaningful risk reduction. Research shows that annual or semi-annual rebalancing captures nearly all the benefits. Set a reasonable schedule and stick to it.
Frequently Asked Questions
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