Many UK investors end up holding funds in an ISA, a pension (whether a workplace scheme or a SIPP), and sometimes a General Investment Account, opened at different times for different reasons. It is tempting to think of each of these as a separate pot with its own investment strategy. In practice, treating them as three fragments of one combined portfolio — rather than three portfolios in their own right — usually leads to better diversification, lower costs, and a more coherent, tax-efficient overall plan.
Why the "three separate pots" mindset causes problems
It is easy to see how the separate-pots approach develops. An ISA might have been opened years ago with a simple global tracker; a workplace pension came with its own limited fund range chosen by an employer; a GIA might have been opened later, once ISA and pension allowances were used up in a particular year. Each account was set up independently, often at different times and for different immediate reasons.
The diversification problem
If each account is diversified on its own terms, the combined result can be far less diversified than it appears. A global tracker in the ISA and a similar global growth fund as the workplace pension default can mean the investor's total savings are much more concentrated in a single style of investing than either account alone would suggest — a form of overlap risk that is easy to miss when reviewing accounts one at a time.
The tax-efficiency problem
Different account types have different tax treatments, and some asset types suit some wrappers better than others. Holding an income-generating bond fund, for example, in a taxable GIA — where the Personal Savings Allowance may already be used up by other savings interest — is generally less tax-efficient than holding the same fund inside an ISA or SIPP, where that income is sheltered. An investor managing each account in isolation may not notice this kind of mismatch.
A combined-portfolio approach
Thinking of ISA, SIPP, and GIA holdings together as one portfolio means deciding on an overall target asset allocation first — for example, a desired split between equities and bonds, or a desired regional spread — and then deciding which specific account should hold which specific fund, based on what is tax-efficient and what is available, rather than trying to replicate the full target allocation inside every single account.
Placing assets by tax efficiency ("asset location")
This principle, often called asset location, suggests holding assets likely to generate more taxable income or gains in the most tax-advantaged wrapper available, and holding more tax-efficient assets (such as a low-yielding global growth fund) wherever capacity remains.
| Asset type | Reason it may suit ISA/SIPP | Reason it may be acceptable in GIA |
|---|---|---|
| Bond funds / income funds | Regular income sheltered from tax | Income taxed as savings/dividend income if unwrapped |
| High-dividend equity funds | Shelters dividends above the £500 dividend allowance | Dividend tax applies above the allowance |
| Low-yield global growth tracker | Still sensible if space allows | Lower income means less annual tax drag if held here |
Working within account limits and availability
In practice, this is not a free choice — a workplace pension typically only offers its own limited fund range, and ISA and pension contributions are capped by annual allowances. The ISA annual allowance is £20,000 across all adult ISA types combined, and the pension annual allowance is £60,000 (or 100% of earnings if lower, tapered for very high earners), with unused pension allowance from the previous three tax years available to carry forward, in the 2025/26 tax year. Asset location is therefore usually a matter of doing the best that can be done within these constraints, not achieving a theoretically perfect split.
Rebalancing a combined portfolio
Once a target overall allocation exists, rebalancing should also be considered across the whole portfolio rather than account by account. If equities have grown to be overweight relative to the target, new contributions can be directed toward bonds or other underweight assets in whichever account is currently receiving contributions, rather than needing to sell down equities in every single account to bring each one back into balance individually.
Why this reduces cost and tax friction
Selling within a GIA to rebalance can trigger a Capital Gains Tax event — the CGT annual exempt amount is £3,000 a year, with rates of 18% for basic rate and 24% for higher/additional rate taxpayers on gains above that in the 2025/26 tax year. Directing new contributions to underweight assets, rather than selling existing GIA holdings, is often a more tax-efficient way to rebalance than would be apparent from looking at the GIA in isolation.
A worked example
Consider a hypothetical investor, Tom, aged 45, with the following: £80,000 in a Stocks and Shares ISA, entirely in a global equity tracker; £120,000 in a workplace pension, split by default between a global equity fund and a bond fund; and £15,000 in a GIA, also in a global equity tracker, built up after using his full ISA allowance one year.
Looking at each account separately, Tom might believe his GIA and ISA together (£95,000) are "all equities" and only his pension has any bonds. Viewed as one combined portfolio of £215,000, his overall equity/bond split is actually determined by how much of the £120,000 pension sits in the bond fund — perhaps 30%, or £36,000 — giving him a combined bond allocation of roughly 17% of his total £215,000 portfolio, not the 0% his ISA and GIA alone might suggest. Recognising this, Tom decides his true target allocation should guide adjustments to his pension's fund split and future ISA contributions together, rather than assuming his ISA needs its own separate bond holding to be "balanced" on its own.
Practical steps for reviewing a combined portfolio
- List every account — ISA, SIPP, other pensions, GIA — and the specific funds held in each, with current values.
- Add up the total value held in each broad asset class (equities, bonds, property, cash) across all accounts combined.
- Compare this combined split against an intended overall target allocation, rather than checking each account individually against that target.
- Identify any obvious tax-location mismatches, such as high-income funds sitting in a taxable GIA while a pension holds a low-yield tracker.
- Decide where new contributions should go based on the whole picture, rather than automatically topping up whichever account is easiest to add to.
Deciding where new money goes first
A related question to asset location is contribution priority — when an investor has spare money to invest, which wrapper should receive it first? There is no single universal answer, since it depends on individual circumstances such as employer pension matching, income tax position, and how soon the money might be needed, but some general principles are widely discussed.
Employer pension matching
Many workplace pensions include employer contributions that increase if the employee contributes more, up to a certain percentage of salary. Contributing enough to receive the full available employer match is often considered before other wrappers, since declining to do so effectively forgives free money regardless of what else the portfolio looks like.
ISA versus further pension contributions
Beyond any employer match, the choice between prioritising further pension contributions or ISA contributions often comes down to a trade-off between the pension's upfront tax relief and reduced flexibility (money is generally inaccessible until a minimum pension age, which is itself scheduled to rise) versus the ISA's tax-free growth and full flexibility to withdraw at any time. Some investors split new contributions between the two deliberately, to build both a pension for later life and an ISA for more flexible medium-term goals.
Family wrappers
Where children are involved, a Junior ISA (JISA) is another wrapper some families use, with its own annual allowance of £9,000 in the 2025/26 tax year, separate from the adult ISA allowance — again best considered as part of a household's overall combined savings and investment picture rather than in isolation.
Keeping track without overcomplicating things
A combined-portfolio view does not require constant, granular monitoring. For most long-term investors, a review once or twice a year — checking the combined asset allocation across all accounts, confirming contribution priorities still make sense, and correcting any glaring tax-location mismatches — is sufficient. The goal of thinking about ISA, SIPP, and GIA holdings together is better-informed decisions at those review points, not a need to actively trade more frequently. Many platforms now offer consolidated reporting tools that show a combined view across accounts held with them, though these will not capture pensions or accounts held elsewhere, so a simple spreadsheet or notes document that an investor updates themselves at each review remains a common and effective approach. What matters most is consistency — reviewing the same set of accounts at the same time each year, using the same method to calculate the combined allocation, so that genuine drift in the portfolio is easy to spot rather than obscured by inconsistent record-keeping between reviews.
Key takeaways
- Treating ISA, SIPP, and GIA holdings as fragments of one combined portfolio, rather than three separate ones, generally leads to better diversification and lower tax drag.
- Asset location — placing income-generating or heavily taxed assets in ISAs and pensions, and more tax-efficient assets wherever space remains — can improve after-tax outcomes.
- Rebalancing by directing new contributions to underweight assets, rather than selling across every account, can reduce both cost and Capital Gains Tax exposure.
- A combined view often reveals that a portfolio's true asset allocation is quite different from what any single account suggests on its own.
- Workplace pension fund ranges and annual allowances constrain how perfectly asset location can be achieved in practice.
- Always check current HMRC and FCA figures for ISA, pension, dividend, and CGT allowances, as these are reviewed and can change.