How do you rebalance a portfolio tax-efficiently?

01 Balance the household, not the account

The portfolio that matters is everything you own added together. An individual account being 90% equities is not a problem if the household position across pensions, ISAs and taxable accounts is at target — and correcting each account separately is how unnecessary tax bills get generated.

That reframing is what makes efficient rebalancing possible. If the taxable account holds the assets you never want to sell and the pension holds the ones you rebalance with, the whole adjustment can happen where no tax arises.

Platform tools rarely show this, because each provider sees only its own accounts. A single spreadsheet listing every holding across every account is the tool this needs, and it takes an hour to build once.

Source: FCA consumer information

02 Inside a wrapper, switching is free

Selling a fund inside a SIPP or a stocks and shares ISA triggers no Capital Gains Tax and no Income Tax, whatever the gain and whatever the size. The wrapper is opaque to the tax system until money leaves it.

So a pension is the natural place to hold the assets that need frequent adjustment, and to absorb whatever correction the household position needs. A 40-point swing inside a SIPP costs nothing but a dealing charge.

The one cost to watch is dealing fees and spreads, which are real if small. Rebalancing quarterly rather than annually multiplies those for very little benefit, and the evidence on rebalancing frequency does not support the shorter interval.

There is a second reason to concentrate the adjustable holdings in a pension rather than an ISA, and it is about what you want to keep. An ISA is the account most likely to be spent early in retirement and the one a surviving spouse can inherit as an additional permitted subscription, so it suits assets you intend to hold. A pension is the account with the longest horizon and the freest internal switching, which makes it the natural home for the part of the portfolio that moves.

Source: Individual Savings Accounts (ISAs)

03 Outside, use flows rather than sales

In a general investment account every sale is a disposal, and gains above the annual exempt amount are taxed at 18% or 24%. The efficient method is to avoid the sale: direct new contributions, dividends and interest to whichever asset is underweight, and let the imbalance correct itself over time.

In drawdown the same logic runs in reverse. Withdrawals can be taken from whichever asset is overweight, which rebalances the portfolio and funds spending in one action. That is the single most useful habit in a decumulation portfolio.

Where a sale is unavoidable, use the annual exempt amount deliberately each year rather than letting it expire, and consider a Bed and ISA so the reacquired holding sits inside a wrapper afterwards.

One rule to know before selling anything outside a wrapper: reacquiring the same holding within thirty days matches the sale against the repurchase, so the gain is not realised as intended. That is what makes a naive sell-and-rebuy pointless, and what a Bed and ISA works around by putting the reacquired holding inside a different account.

On the defaults above, the worked example shows £2,640. The same switch inside a pension or ISA would cost nothing at all, so this is the price of rebalancing in the wrong account.

Source: Capital Gains Tax allowances

04 Spouses and the second set of allowances

Transfers between spouses and civil partners are made at no gain and no loss, so an asset can be moved to whichever partner has the unused annual exempt amount or the lower Capital Gains Tax rate before it is sold. That doubles the exempt amount available to the household each year.

The transfer has to be a genuine outright gift — the asset becomes theirs, and it is theirs in a divorce and in their estate. That is the real cost of the technique and it should be understood rather than glossed over.

Used alongside the two personal allowances, it makes the household the right unit for tax planning in almost every case.

Source: Capital Gains Tax rates

05 A workable annual routine

Once a year, list every holding across every account and compute the household allocation. Decide the correction needed. Make it inside the pension first, then inside the ISA, and only then consider a taxable sale.

Then check the annual exempt amount: if it is unused and there are gains available, realise them deliberately, because it does not carry forward. Reinvest through an ISA subscription where allowance remains.

Once a year is enough. Rebalancing more often adds cost and dealing spreads without improving outcomes, and the tolerance band that triggers action matters more than the calendar — a five-point drift is noise, a fifteen-point drift is not.

Source: MoneyHelper: ISAs