The Box Theory · Iain Ford · FEP&G Ltd · 2026/27

Every wrapper is just
a better box

Three questions answer everything: what happens when you put money in, what happens inside the box, and what happens when you take it out.

ⓘ About this guide
Tax rules shown are for the 2026/27 tax year and are subject to change. Further significant changes take effect from April 2027. Each wrapper gives a conceptual overview — qualifying conditions for EIS, VCT, and investment bonds are more detailed than any summary can capture. For educational purposes only — not financial, tax, or legal advice.
The journey — from under the bed to a better box
The journey from under the bed to tax-efficient wrappers A cartoon showing a bed with money underneath on the left, then progressively larger and better labelled boxes moving right — ISA, Pension, Specialist — with arrows showing the path toward increasing tax efficiency £ £ £ 👻 HMRC Under the bed No protection Cash / S&S ISA ISA Tax-free growth Pension Pension Relief + growth ★ EIS / VCT / Bond £ Specialist Max efficiency Increasing tax efficiency
Putting money in

Do you get a tax advantage at the point of contribution? Pensions and EIS/VCT top up what you put in. ISAs receive no relief but protect everything inside.

Inside the box

Does growth compound without tax drag? Most wrappers shelter interest, dividends, and gains completely. This is where the long-term power comes from.

Taking money out

Can you access it freely, and is it taxed on exit? ISAs are fully flexible and tax-free. Pensions have age restrictions but offer a 25% tax-free lump sum.

Under the bed

Keeping money with no tax wrapper. Every penny of interest, gain, or dividend is exposed to tax.

No wrapper — avoid this
Putting money in
  • Money you have already paid tax on
  • No tax relief, no bonus — what you put in is simply what you have
  • No tax event on the deposit itself — the problem starts once the money begins to earn
Inside the box
  • Interest taxed above Personal Savings Allowance (£500–£1,000/yr)
  • Capital gains taxed above £3,000 CGT exemption (18% basic, 24% higher rate)
  • Dividends taxed above £500/yr — 10.75% basic, 35.75% higher, 39.35% additional rate
  • Inflation erodes real value year on year
Taking money out
  • Withdraw anytime, no restrictions
  • No tax on the withdrawal itself
  • But gains were taxed throughout — full exposure
Putting in
No benefit
Inside
Fully taxed
Taking out
Free access
Putting the boxes to work — why it depends, and why that matters
There is no universal right answer
The boxes above are tools. Which ones to use, in what order, and in what combination depends entirely on the individual. The same £1,000 could be better placed in a pension, an ISA, a bond, or left accessible — and the right answer changes depending on who you are, where you are in life, and what you are trying to achieve. The purpose of this section is not to tell you what to do. It is to show you all the variables that need to be considered at once — because that is the only honest way to approach it.
The variables that shape the decision
💷
Your tax rate now — and your expected tax rate later A pension is most powerful when you contribute at a high rate and withdraw at a lower one. If your tax rate in retirement is likely to be the same or higher, the pension advantage shrinks. An ISA, by contrast, has no tax on the way out regardless of your future rate — which matters if you expect your income to rise. The spread between your current and future marginal rate is one of the most important variables in the whole decision.
⏱
Your time horizon — and when you need access A pension locks money away until age 57. An ISA gives access anytime. An EIS locks you in for a minimum of three years. A LISA penalises early withdrawal. The longer your horizon, the more powerful the compounding effect of any wrapper — but only if you can leave the money alone. Liquidity needs are a real constraint that cannot be ignored in favour of tax efficiency alone.
🏢
Whether an employer contribution is available An employer pension match is the only wrapper where someone else adds money to your pot as a condition of you contributing. That makes it categorically different from every other box — it is not just tax-efficient, it is an immediate guaranteed return before any investment growth. The size of that match, and whether salary sacrifice is available, changes the arithmetic significantly.
🏦
What you already hold — and in which boxes Someone with a large existing pension pot and no ISA savings faces a different decision to someone with the reverse. Someone with significant gains sitting outside any wrapper has a CGT planning opportunity that someone starting from scratch does not. The right next step depends heavily on what already exists — the current state of the whole picture, not just where to put new money.
🏡
Estate and inheritance tax position Pensions currently sit outside your estate for inheritance tax purposes — making them a powerful IHT planning tool as well as a retirement vehicle. ISAs do not. Investment bonds can be written in trust. EIS shares may qualify for Business Relief. The interaction between wrapper choice and estate planning is a material variable for anyone with an IHT exposure, and it changes the order of priority significantly.
📊
Income needs in retirement — and how the boxes interact Drawing from a pension, an ISA, and taxable savings in the wrong sequence can push you unnecessarily into a higher tax band, erode your personal allowance, or trigger the high-income child benefit charge. Drawing in the right sequence — and from the right boxes at the right time — can mean the same pot of money generates materially more net income over a retirement. This is not a single decision; it is an ongoing strategy.
Why this leads to cash flow modelling
No single variable above can be optimised in isolation. Change one and it affects the others. A higher pension contribution reduces take-home pay today but changes the retirement income picture. Drawing the ISA before the pension in retirement preserves the pension's IHT shelter but may mean paying more tax in later years. These interactions cannot be seen clearly in a list — they can only be seen clearly in a single frame that shows all the moving parts together across time.

That is what a cash flow model does. It takes all of the boxes, all of the variables, and all of the timelines and maps them into one picture — showing what the plan looks like year by year, what happens under different scenarios, and where the decisions that matter most actually sit. It turns an abstract question ("which box?") into a visible, navigable answer ("here is your picture, here are your choices, here is the cost of each one").

The boxes in this guide are the building blocks. A cash flow plan is how you use them together.

Why does tax efficiency matter?

The same money. The same returns. A different box. Watch what happens over time.

Growth model
Annual rate divided by 12 and compounded monthly. Real returns are volatile — markets rise and fall.
Simplification
Tax drag method
Tax modelled as a reduced net return rate. In reality tax depends on the split between interest, dividends, and gains and when each is crystallised.
Simplification
Constant growth rate
Same return every year with no volatility. Real portfolios experience up and down years. Sequence-of-returns risk is not captured.
Important
Constant tax rate
Marginal rate fixed for the entire period. In practice rates change with income, employment status, and policy.
Simplification
Zero charges
No platform fees, fund charges, or adviser costs. Real charges typically 0.5–1.5% p.a. and compound significantly over time.
Important
Inflation not applied
All figures in nominal terms. Real purchasing power will be lower depending on inflation during the period.
Note
Contributions
Equal monthly contributions throughout. No allowance for salary growth, pauses, or years where allowances are exceeded.
Simplification
Drawdown model
Final pot divided equally over 20 years with no further growth. Pension estimate applies flat 20% effective rate on 75% of pot.
Important
Good for: illustrating the directional impact of tax drag on long-term compounding.  |  Not: a financial plan, projection, or forecast.
£20,000
£500 / month
6%
25 years
40% — higher rate taxpayer
Tax-efficient box
—
Full growth retained
Outside any box
—
Tax paid each year
Lost to tax drag
—
—
Tax-efficient box
Outside any box
Contributions

Drawdown over 20 years — what does the pot actually pay?

ISA / tax-efficient box
—
per year, fully tax-free
Outside any box
—
per year after ongoing tax
Pension (25% free, 75% taxed)
—
per year (est. 20% avg withdrawal tax)
Annual income lost to tax drag
—
per year less vs tax-efficient box

All figures illustrative only. Not financial advice. Constant growth, zero charges, nominal figures, equal monthly contributions, simplified drawdown. Always seek FCA-regulated financial advice.

All boxes at a glance

Side-by-side
comparison

Every major UK tax wrapper — what happens going in, inside, and coming out.

ⓘ 2026/27 tax year — rules subject to change
Key changes for 2026/27: dividend tax rates rise to 10.75% (basic) and 35.75% (higher rate). VCT income tax relief reduced from 30% to 20%. CGT rates unchanged at 18% and 24%.

Coming April 2027: Pensions brought within IHT. Cash ISA limit reducing to £12,000 for under-65s. Savings tax rates increasing. The 2026/27 year is a material planning window.
All UK tax-efficient wrappers compared
WrapperPutting inInsideTaking outBest for
Under the bedAfter-tax cashFully taxed gainsFree, anytimeAvoid — use a box
Cash ISAAfter-tax, up to £20k/yrTax-free interestFree anytime, tax-freeShort-term savings
Stocks & Shares ISAAfter-tax, up to £20k/yrTax-free growth & incomeFree anytime, tax-freeLong-term investing
Lifetime ISAAfter-tax + 25% bonusTax-free growthTax-free (home / age 60+)First home or retirement
Personal Pension (SIPP)20–45% tax relief upliftTax-free growth25% free; rest taxed as incomeRetirement saving
Workplace PensionPre-tax + employer matchTax-free growth25% free; rest taxed as incomeAlways fill first
Onshore BondAfter-tax, no limitTax-deferred (20% paid)Top-slicing relief may applyIncome deferral / estate
Offshore BondAfter-tax, no limitFull gross roll-upIncome tax on encashmentHigher-rate tax deferral
EIS30% income tax reliefCGT-free growthCGT-free after 3 yearsHigh-risk / tax planning
VCT20% income tax reliefTax-free dividendsCGT-free; hold 5+ yearsIncome-focused high-risk
Premium BondsAfter-tax, up to £50kTax-free prize drawsFree anytime, tax-freeSafe, tax-free cash

For illustration only. 2026/27 tax year. Subject to change. Not financial advice.

Tax efficiency at a glance

Which taxes does
each box shelter?

A traffic light view across every wrapper and every major UK tax. Green = sheltered. Amber = partial or deferred. Red = exposed.

ⓘ How to read this matrix
Green means the wrapper provides full shelter from that tax. Amber means partial, conditional, or deferred efficiency. Red means no particular protection. The planning complexity column shows how much there is to understand and keep on top of for each wrapper.
Efficient — fully sheltered
Some efficiency — partial, deferred, or conditional
Exposed — tax applies normally
Wrapper Income tax on contributions Income tax on growth / income Capital gains tax Dividend tax Tax on withdrawal Inheritance tax National Insurance Planning complexity (BCM)
Under the bedExposedExposedExposedExposedN/AIn estateExposedNone — but fully exposed to all taxes
Cash ISAAfter-tax inTax-freeTax-freeTax-freeTax-freeIn estateExposedLow — allowance management only
S&S ISAAfter-tax inTax-freeTax-freeTax-freeTax-freeIn estateExposedLow — allowance and investment selection
Lifetime ISA25% bonusTax-freeTax-freeTax-freeTax-free ¹In estateExposedMedium — qualifying use rules, penalty risk
Pension (SIPP)Relief 20–45%Tax-freeTax-freeTax-free25% free; rest taxedOutside estate ²Salary sacrifice saves NIMedium — drawdown sequencing, LTA legacy, IHT from 2027
Workplace pensionRelief + employerTax-freeTax-freeTax-free25% free; rest taxedOutside estate ²Salary sacrifice saves NIMedium — scheme rules, employer match, consolidation
Onshore bondAfter-tax inDeferred (20% paid)DeferredDeferredTop-slicing may applyTrust planning possibleExposedHigh — top-slicing, segment strategy, trust interaction
Offshore bondAfter-tax inDeferred (gross roll-up)DeferredDeferredTop-slicing may applyTrust planning possibleExposedHigh — encashment timing, residency, top-slicing, trust
EIS30% reliefTax-free (3yr+ hold)Tax-free (3yr+ hold)Tax-freeCGT-free exitBPR after 2 yrs ³ExposedSpecialist — qualifying conditions, hold periods, BPR, deferred CGT
VCT20% reliefTax-free dividendsTax-freeTax-freeCGT-free exitIn estateExposedSpecialist — 5yr hold, relief clawback, illiquidity risk
Premium BondsAfter-tax inTax-free prizesN/AN/ATax-freeIn estateExposedLow — capital limit and prize rate awareness only

¹ LISA withdrawals are tax-free for qualifying purposes (first home purchase or age 60+). Early withdrawal for any other reason incurs a 25% government penalty, which claws back the bonus and a portion of your own money.
² Pensions are currently outside the estate for IHT purposes. This changes from 6 April 2027 when pension death benefits will be brought within the IHT regime — a significant planning consideration for the 2026/27 tax year.
³ EIS shares may qualify for Business Property Relief (IHT shelter) after 2 years. BPR has been restricted from April 2026 — the scope of assets qualifying for 100% relief has been reduced and capped at £1m. Seek specific advice on the current position before relying on BPR for any EIS investment.
Tax rules correct for the 2026/27 tax year. Subject to change. This matrix is a simplified overview only — qualifying conditions for each wrapper are more detailed than any grid can capture. Not financial advice.

The Box Theory · Iain Ford · FEP&G Ltd

Planning complexity —
the Box Complexity Measure

Select the boxes that apply to you to see the combined BCM profile — and understand why managing this well is rarely simple.

ⓘ The BCM principle — Box Complexity Measure
Under the Box Complexity Measure (BCM) framework, the wrappers you hold are a direct indicator of how much planning complexity you are carrying. Holding only ISAs needs allowance management. Holding a pension, an offshore bond, and EIS investments brings simultaneous obligations across income tax timing, CGT deferral, top-slicing calculations, BPR qualifying periods, and IHT planning — all of which interact. The BCM makes that complexity visible in one frame.
Select the wrappers you hold — see your combined BCM profile
Select at least one wrapper above to see the BCM profile.

BCM ratings are illustrative. Individual circumstances will affect actual complexity. For educational purposes only. FEP&G Ltd · 2026/27 tax year. Not financial advice.