Key takeaways
- Moving £20,000 of UK shares into an ISA costs £108.45 in visible charges at one large platform: a £6.95 dealing fee, £100 of stamp duty and a £1.50 levy. The tax is separate.
- On an £8,000 embedded gain, £3,000 falls inside the 2026 to 2027 annual exempt amount and £5,000 is taxable. That is £1,200 at 24%, or £900 at 18%.
- At the FTSE All-Share's 3% yield, £20,000 pays £600 of dividends a year. Sheltering that saves £214.50 of tax annually at the higher rate, £64.50 at the basic rate.
- Those savings repay the £108.45 of charges in about 6 months at the higher rate. Repaying the whole £1,308.45 takes 6.1 years, or 20.29 years at the basic rate.
- The £500 dividend allowance already covers the first £16,667 of holdings at a 3% yield, so below that the income half of the trade saves nothing.
The bill lands today and the saving arrives in instalments
You hold shares outside a tax wrapper, they have risen, and you are wondering whether to move them into an ISA. The manoeuvre has a nickname, bed and ISA, and the question people actually type is whether the tax saved later covers the tax paid now.
Here is the shape of it. A bed and ISA is one sale followed by one repurchase. The holding leaves a dealing account and comes back inside a stocks and shares ISA. That sale is a disposal for capital gains tax, so any gain above the annual exempt amount is taxable in the year you do it. In return, every future gain and every future dividend on that holding falls outside the tax system.
It's a known cost today against an unknown saving later. Three things decide it: the size of the embedded gain, the income the holding produces, and how long you'd keep it. On the figures below the dealing costs are trivial and repay themselves inside a year for a higher-rate taxpayer. The capital gains tax is the part that can take 6 years to earn back, and in one common case never does.
Shares can't be posted into an ISA, which is why a sale has to happen
Bed and ISA exists because of one condition in the ISA Regulations. Regulation 4 defines a qualifying account as one "to which the qualifying individual subscribes only by payment to the account manager of a sum or sums of the individual's cash". Cash. Not shares.
There is no route that hands the existing shares across intact. They have to be sold, the cash subscribed, and the same shares bought again inside the wrapper. Hargreaves Lansdown says so on its own service page: "Usually, you're not able to move shares directly into a pension or an ISA due to HMRC rules."
Once inside, the exemption is wide. Regulation 22 says no tax is chargeable on the investor "in respect of interest, dividends, distributions or gains in respect of account investments". HMRC's guidance for ISA managers repeats it and adds the half people forget: "losses on ISA investments cannot be allowed for Capital Gains Tax purposes against capital gains outside an ISA." The wrapper takes the losses too. What else the wrapper does and doesn't do is set out in our guide to the ISA rules that bite.
The 30-day rule doesn't catch the repurchase, and it hangs on one clause
Sell shares and buy the same ones back within 30 days, and HMRC matches the sale to that repurchase rather than to your pooled cost. The effect is normally to wipe out the gain you were trying to crystallise. If it applied here, a bed and ISA would achieve nothing at all.
It doesn't apply, and the reason is narrower than most explanations admit. HMRC's Capital Gains Manual lists three requirements for the rule to bite: shares "of the same class", "acquired by the same person in the same capacity", and "acquired within the 30 days after the disposal." Section 106A of the Taxation of Chargeable Gains Act 1992 carves capacity out explicitly: "where a person disposes of securities in one capacity, they shall not be identified under those provisions with any securities which he holds, or can dispose of, only in some other capacity."
An ISA is a different capacity. Regulation 4 requires that "the title to all account investments shall be vested in the account manager or his nominee", while beneficial ownership stays with you. You keep the economics and give up the legal title.
The published support for that reading is thinner than the confidence around it. HMRC illustrates the capacity limb exactly once, with a trust: "a disposal by an individual in a personal capacity followed by an acquisition as trustee of a trust would not be subject to the rule." There is no published ISA example. A Capital Gains Manual page number circulates online as the authority for the ISA case, and that page does not exist. The full matching order, and what happens when it fires, is in our piece on the UK share matching rules.
The visible cost of moving £20,000 is £108.45
Take a holding worth £20,000, which is the whole ISA subscription limit for the 2026 to 2027 tax year, bought for £12,000. It carries an £8,000 gain. Put it through Hargreaves Lansdown's Share Exchange, the platform's name for the paired trade, and the charges are published: "No charge for selling the shares in your Fund and Share Account", then "a dealing charge of £6.95 (or less for frequent traders) to buy shares back in the ISA or SIPP".
Stamp duty is the larger line. GOV.UK is blunt about it: "When you buy shares, you usually pay a tax or duty of 0.5% on the transaction." On a £20,000 repurchase that is £100. Add the Takeover Panel levy, because "for trades over £10,000, you'll also pay the standard £1.50", and the visible cost is £108.45. That is 0.54% of the holding.
Two exemptions are worth knowing. Stamp duty doesn't reach funds, because GOV.UK excludes anyone who buys "units in a unit trust from the fund manager" or an OEIC from the manager. And AJ Bell's paired deal doesn't cover funds either: its Bed and ISA "does not include Pacific Rim-listed shares or investment funds". For those, it is two separate trades, two dealing charges, and a genuine gap between the legs.
Tax dwarfs the charges, and the gap widens with the embedded gain
Now the tax. The annual exempt amount for the 2026 to 2027 tax year is £3,000, so an £8,000 gain leaves £5,000 taxable. Rates from 6 April 2026 are "18% and 24% for individuals" — 18% where the gain still sits inside the £37,700 basic rate band once added to taxable income, 24% above it. So £1,200 for a higher-rate taxpayer and £900 for someone whose gain stays inside the band.
Total up-front cost at the higher rate: £1,308.45 on a £20,000 holding. The chart above plots that total against the size of the embedded gain, and the shape carries the argument. With no gain, or a gain inside £3,000, the cost is the flat £108.45. At a £5,000 gain it is £588.45. At £15,000 it is £2,988.45. Almost every pound of the variation is tax, and none of it is the platform.
What the wrapper buys is £214.50 a year on £20,000
The FTSE All-Share yielded 3% as at 31 July 2026, on FTSE Russell's own factsheet. A £20,000 holding at that yield pays £600 of dividends a year.
Outside a wrapper, dividends above the allowance are taxed. GOV.UK: "You also get a dividend allowance of £500 each year." From 6 April 2026 the rates are 10.75% at the basic rate, 35.75% at the higher rate and 39.35% at the additional rate. Inside a wrapper there is nothing to pay: "You do not pay tax on dividends from shares in an ISA."
If the £500 allowance is already spent on other holdings, sheltering that £600 saves £214.50 a year at the higher rate, £64.50 at the basic rate and £236.10 at the additional rate. Those are marginal figures, and they are the ones that matter once the allowance is gone. The rate structure underneath them is in our guide to UK dividend and savings tax.
Payback is 6 months on the charges and 6.1 years on the whole bill
Set the saving against the cost. £108.45 of dealing costs against £214.50 a year of dividend tax saved is a payback of roughly 6 months. Against £64.50 at the basic rate it is 1.68 years. On friction alone the trade clears its cost quickly for almost anyone whose dividend allowance is exhausted.
The whole bill is a different question. £1,308.45 against £214.50 a year is 6.1 years. At the basic rate it is 20.29 years. That is the number worth holding in mind, and it is why the size of the embedded gain matters far more than any line on a platform's tariff.
Treating the £1,200 as a pure cost overstates it, though. The same tax would fall due on any future sale outside the wrapper, so what you have really bought is timing: the tax arrives now rather than later, and you forgo the return on that £1,200 in between. On a gain you would have realised eventually anyway, the honest cost of a bed and ISA is the £108.45 plus whatever that prepayment would have earned.
The cost you can't see is the price the deal gets struck at
Three costs appear on no tariff.
The first is the spread, the gap between the price to sell and the price to buy. AJ Bell names it: "any difference between the investment's buying and selling price (also known as the bid-offer spread) should also be factored in". Hargreaves says it aims "to place the trade at the mid-point between the price to sell and repurchase shares", which removes the spread when it works.
The second is timing. Hargreaves states the instruction "can take up to four working days". AJ Bell reserves "up to 10 working days to place your Bed and ISA deal", with "the price dealt" being "the price at the time of the transaction". You stay invested throughout, so this isn't an out-of-market gap in the usual sense. What you don't control is the price the gain gets struck at, and therefore the size of the tax bill. In the 12 months to 31 July 2026 the FTSE All-Share returned 21.6% with annualised volatility of 11.0% and a peak-to-trough fall of 9.1%. A 9.1% move on £20,000 is £1,820, which is more than the entire tax bill in the example above.
The third is share count. Both platforms say the same thing in different words: you end up with slightly fewer shares, because the charges come out of the proceeds. Interactive Investor lists what it deducts before repurchasing — "Trading fees on the repurchase", "Stamp Duty on the repurchase (0.5% on most UK shares)" and "Any price movements between the sale and purchase price".
The platform charge usually doesn't move, which surprises people
The custody charge is the cost people expect to rise, and on these platforms it doesn't. Hargreaves states it directly: "the annual charge for holding shares in the HL Stocks and Shares ISA or SIPP is the same as in the Fund and Share Account (0.35% per year capped at £12.50 per month for each account)". AJ Bell's ceiling is lower still, and it applies to the account rather than the wrapper: "Never pay more than 0.25%".
So on these two tariffs the wrapper is free to hold. Where a platform does price an ISA above a dealing account, that difference is a recurring cost, and it has to be netted off the tax saved before any payback figure means anything. The crossover between flat and percentage charging is worked through in our piece on platform fees.
It starts paying at £16,667 of holdings, not at a round portfolio number
The threshold most people miss isn't a portfolio size in the abstract. It is whether the two allowances are already spent.
At a 3% yield the £500 dividend allowance covers the first £16,667 of unwrapped holdings. Below that, if those are your only dividends, the income half of a bed and ISA saves precisely nothing, and the £108.45 plus any capital gains tax buys a benefit that only starts later.
The capital gains side has the same structure. Gains are taxable only above £3,000 a year, and only when a disposal happens. Someone who realises less than that each year, on purpose, pays no capital gains tax without any wrapper at all.
Above those thresholds the arithmetic turns quickly, because the allowances don't scale with the portfolio. A £100,000 unwrapped holding at a 3% yield throws off £3,000 of dividends, of which £500 is sheltered and the rest isn't. Moving all of it takes 5 tax years at £20,000 a year, and £20,000 is the limit for the 2026 to 2027 year.
The strongest objection: if you never sell, the tax was never due
Here is the case against, and it is stronger than the marketing allows. Capital gains tax paid on a bed and ISA is only a saving if you would otherwise have paid it. Section 62 of the Taxation of Chargeable Gains Act 1992 says the assets of a deceased person "shall not be deemed to be disposed of by him on his death", and are acquired by the personal representatives "for a consideration equal to their market value at the date of the death".
That is the part that matters. A holding kept until death has its gain wiped rather than taxed. For someone with no intention of ever selling, crystallising £8,000 of gain to pay £1,200 today buys nothing on the capital gains side at all. The only benefit left is dividend tax, £214.50 a year at the higher rate, and the payback stretches back out to 6.1 years.
Two further objections. Losses inside an ISA are disregarded, so a holding you might want as a realised loss to set against other gains is worth more outside the wrapper. And the crystallised gain adds to your total gains for the year, which can fill the £37,700 band and push other disposals from 18% to 24%.
What these numbers can't settle
The limitations here are real and several.
The yield is one date's snapshot. The FTSE All-Share yielded 3% on 31 July 2026; a portfolio of growth shares might yield a fraction of that. Every payback figure above scales inversely with yield, and a holding that pays no dividends saves nothing on income, so the dividend payback never arrives.
The charges are two platforms' published tariffs on one date, not the market. They differ from each other already, and a third platform could change the friction figure materially.
Nothing here forecasts. The 21.6% 12-month return and 11.0% volatility describe the year to 31 July 2026 and say nothing about the next one. Tax rates aren't fixed either: the annual exempt amount was £12,300 in the 2022 to 2023 tax year against £3,000 now, and that cut is a large part of why the question comes up at all. A future government could move it in either direction and the whole calculation moves with it.
And the capacity argument rests on a reading of one statutory clause that HMRC has never illustrated for ISAs. Platforms operate on that reading at scale, which isn't the same thing as a published ruling.
What would change the conclusion
If the dividend allowance rose materially above £500, the income half of the trade would shrink for most people, and the payback on any crystallised gain would lengthen with it.
If capital gains tax rates fell from 18% and 24%, the up-front bill would fall too and the case would strengthen — the mirror image of what happened when the annual exempt amount was cut from £12,300 to £3,000.
And if you are confident you would never sell, the capital gains element stops being a prepayment and becomes a real cost, leaving only the dividend arithmetic standing. That single assumption moves the answer further than any charge on any tariff.
The figure to watch isn't the ISA deadline. It is the embedded gain sitting in each holding, and how much of the £3,000 exempt amount this tax year has already absorbed, because that is what decides whether the move costs £108.45 or £1,308.45. LedgerTouch tracks unrealised gain lot by lot, which is the number the whole calculation turns on.