Bestinvest vs AJ Bell: The Fee Breakdown That Shows Which ISA Platform Is Actually Cheaper

AJ Bell runs two tier tables. Funds pay 0.25% on the first £250,000, then 0.10% between £250,000 and £500,000, then zero above £500,000. Shares and ETFs pay a percentage fee that is capped at £3.50 per month — £42 a year, regardless of whether you hold £20,000 or £2 million.

Bestinvest runs four tier tables, split by investment type before balance tiers even kick in. On Ready-made Portfolio funds and US shares, the fee starts at 0.20%. On everything else — third-party funds and UK shares — it starts at 0.40%. Both investment-type tiers then drop to 0.10% between £500,000 and £1 million, and to zero above £1 million. The 0.40% tier also has an intermediate step to 0.20% between £250,000 and £500,000.

In plain English: Bestinvest's published 0.40% is the maximum rate, not the uniform rate. Anyone buying US-listed ETFs, using ready-made portfolios, or running a seven-figure portfolio pays materially less than the sticker.

Here is the annual platform-fee bill for a fund-only ISA at five sizes:

At £500,000, AJ Bell's total is £875 (£625 on the first £250k plus £250 on the next). Bestinvest's is £1,500 (£1,000 on the first £250k plus £500 on the next). On UK funds, AJ Bell stays ahead at every size under £500,000. Above £500,000, AJ Bell charges zero on funds while Bestinvest charges 0.10% — flipping the comparison hard in AJ Bell's favour for seven-figure fund investors.

Anyone building a globally diversified ISA usually holds some US exposure — an S&P 500 tracker, a NASDAQ ETF, a US-listed sector fund. Most comparison articles price these at Bestinvest's 0.40% rate. They shouldn't.

Bestinvest's service fee on US shares is 0.20% up to £500,000, dropping to 0.10% and then to zero on the standard tiers above. Hold £50,000 of US ETFs and the Bestinvest service fee is £100 a year — half what a fund at the same balance would cost. On £100,000, it is £200.

AJ Bell handles the same US ETFs differently. Because ETFs sit on the shares account — not the funds account — they benefit from the £3.50-per-month cap. At £100,000 of US ETFs, AJ Bell charges £42 a year. At £500,000, still £42. That's a £158 gap at £100k, a £958 gap at £500k.

Both platforms charge FX on purchase and sale, but that only hits twice — when you buy and when you eventually sell. AJ Bell's international dealing charge is 0.75% (capped per transaction). Bestinvest charges 0.95% with no stated cap, but waives the £4.95 dealing fee on US shares.

One nuance most readers miss: for a buy-and-hold US ETF investor who never sells, the 0.20% vs 0.75%/0.95% spread matters far less than the ongoing service fee. Bestinvest's 0.20% annual rate on US shares is genuinely competitive — it just isn't as cheap as AJ Bell's flat £42 cap once your US holdings exceed roughly £17,000.

Bestinvest charges £0 for every fund buy, sell, dividend reinvestment, regular investment and limit order. AJ Bell charges £1.50 per fund trade, £1.50 for regular investing, and £1.50 for dividend reinvestment.

UK share dealing runs £4.95 at Bestinvest and £5.00 at AJ Bell — or £3.50 at AJ Bell if you placed 10 or more share deals the previous calendar month. That headline is close to even, but the fund side is where activity compounds.

Take the most common active investor profile: a £75,000 fund ISA with four trades a month (rebalance two positions, switch two others). At AJ Bell, that's £125/12 × 75,000 × 0.0025 — £188 platform fee plus 48 × £1.50 = £72 in dealing fees. Total: £260 a year. At Bestinvest: £300 platform fee plus £0 dealing. Total: £300 a year. AJ Bell still wins by £40.

At eight fund trades a month, the AJ Bell dealing bill rises to £144. Total: £332 versus Bestinvest's flat £300. Bestinvest pulls ahead.

The break-even is roughly seven fund trades per month on a £75,000 portfolio — or proportionally fewer at higher balances, because the platform-fee gap is absolute not proportional. Buy-and-hold investors who rebalance annually will never approach this threshold. Fund switchers chasing momentum, running tactical strategies, or trimming positions to keep within a target allocation every few weeks will.

The regular-investor angle favours AJ Bell by less than people think. Regular investing charges £1.50 per trade at AJ Bell and £0 at Bestinvest. A saver drip-feeding £200 a month into three funds pays £54 a year at AJ Bell and nothing at Bestinvest — a real gap, but small relative to platform fees on anything above £25,000.

For hands-off investors who pick a single managed portfolio and leave it alone, Bestinvest genuinely undercuts AJ Bell. The service fee drops to 0.20% from pound one — five basis points below AJ Bell's 0.25%. At £100,000, that's £200 a year versus £250.

But platform fee is only half the total cost of a ready-made product. The other half is the ongoing charges figure — the OCF — charged by the underlying fund manager. Bestinvest's own fees-page illustration uses an indicative 0.35% OCF on its Smart funds range. AJ Bell's Ready-Made Portfolios carry fund-level OCFs that typically sit in the same 0.15% to 0.50% range depending on whether you pick the Cautious, Balanced or Adventurous mix — see the breakdown in our AJ Bell Ready-Made Portfolios review.

Stacking platform plus OCF on a £50,000 ready-made ISA:

• Bestinvest Smart funds: £100 platform + £175 OCF = £275 a year (0.55% total cost)
• AJ Bell Balanced RMP (assuming 0.31% OCF): £125 platform + £155 OCF = £280 a year (0.56% total cost)

The difference is functionally zero. Bestinvest's 0.05% platform advantage is real but gets swallowed by OCF variation between the specific fund ranges. If you are choosing a ready-made portfolio based on fee alone, the underlying fund OCF matters more than the platform headline — yet most comparison articles fixate on the 0.20% vs 0.25% and call it for Bestinvest.

Both platforms pay you interest on uninvested cash. The rates are a mile apart.

Bestinvest pays 2.98% AER (as of 29 December 2025) on all cash balances, across ISAs, SIPPs and Investment Accounts. AJ Bell pays 1.75% AER on ISA and Lifetime ISA cash (since 1 February 2026). SIPP cash earns 2.05% up to £100,000 and 2.40% above it.

The Bank of England base rate has sat at 3.75% since the 18 December 2025 MPC meeting. Bestinvest's 2.98% is 0.77 points below base. AJ Bell's 1.75% on ISA cash is 2.00 points below base.

For an investor between decisions with £20,000 of cash in their ISA, the gap is £596 vs £350 — £246 a year. For a pensioner running a £100,000 ISA with a heavy cash allocation for sequence-risk reasons, the gap is £2,980 vs £1,750 — £1,230 a year. That is larger than the entire platform-fee bill at most portfolio sizes.

Neither platform matches the best cash ISAs on the market right now — a dedicated cash ISA will generally pay more. But if you are holding cash on-platform to deploy when opportunities arise, Bestinvest's rate is materially better. Over the two years the Bank Rate has been cutting, neither platform has passed through cuts symmetrically; expect rates to shift without notice.

Bestinvest offers a flexible ISA. Under HMRC rules, flexible ISAs let you withdraw money and replace it within the same tax year without it counting against the annual £20,000 allowance. Stocks and shares ISAs are not required to be flexible — each provider chooses. AJ Bell's is not flexible.

That asymmetry matters more than fees for a specific cohort: people using their ISA as a medium-term savings vehicle rather than a retirement pot. Career-break bridging, deposit-saving, absorbing a year of low income — these are the scenarios where the ability to withdraw and replace £10,000 without burning allowance is worth real money. For everyone else, ISA flexibility is theoretical.

AJ Bell wins decisively on the Lifetime ISA, which Bestinvest does not offer. The 25% government bonus is worth up to £1,000 a year on the £4,000 maximum contribution. If you're under 40 and saving for a first home or retirement, that £1,000 outweighs any platform-fee difference discussed here — and the LISA vs SIPP trade-off is worth reading before you commit.

Bestinvest offers free investment coaching with no session limit. These are not sales calls — they're genuine guidance sessions that explain fund choices, ISA allowances and withdrawal mechanics to anyone who asks, client or not. Paid Portfolio Health Check advice costs £495 (VAT included) for a one-off plan. AJ Bell offers customer support but not free advisory sessions.

AJ Bell covers ISA and SIPP exit fees from a previous provider up to £500 — but only if your transferred balance is £20,000 or more. Bestinvest does not match that offer but charges nothing for transfers in. For anyone escaping a legacy platform with chunky exit fees, the AJ Bell incentive is worth up to a year's platform costs on a £50,000 ISA. Both platforms are FCA-authorised and covered by FSCS investment protection up to £85,000 per person per firm for custody cash and investments. That is the investment limit — not the £120,000 deposit-protection threshold that went live for banks and building societies on 1 December 2025.

Fees reverse direction depending on what you hold, so the verdict depends on which description sounds like you.

Fund-only ISA under £100,000, rarely trading. AJ Bell wins. At £50,000 the gap is £75 a year in platform fees; dealing charges barely register for someone rebalancing once or twice a year. Total cost difference over a decade: several hundred pounds, compounded.

Global ETF portfolio of any size. AJ Bell wins decisively. The £3.50-per-month cap on shares means £42 a year covers a £20,000 ETF portfolio and a £500,000 ETF portfolio. Bestinvest's 0.20% US-share rate looks competitive until you plot it against a flat £42.

Ready-made portfolio investor. Close enough to ignore. Bestinvest wins the platform-fee column, AJ Bell's OCFs can match or beat depending on the specific strategy. Choose on the portfolio you want, not the platform wrapper.

Active fund switcher making five or more fund trades a month. Bestinvest wins. Free fund dealing erases what used to be a £90+ annual bill at AJ Bell. The 0.15% platform gap becomes secondary above five trades a month.

Fund-heavy ISA over £500,000. AJ Bell wins on fee structure: zero platform fee above £500,000 on funds versus Bestinvest's continuing 0.10% tier up to £1 million. The gap compounds from about £625 a year at £1m in favour of AJ Bell.

Cash-heavy ISA where you park proceeds between decisions. Bestinvest wins. The 1.23-point gap on cash interest funds the higher platform fee on any portfolio up to about £80,000 of invested assets — and above that still comes out net positive if cash is a meaningful slice.

Under-40 saving for a first home. AJ Bell wins by default. Bestinvest has no Lifetime ISA; the £1,000 government bonus cannot be replicated with any fee saving.

Neither platform is universally cheaper. The published 0.40% vs 0.25% is the worst possible shorthand for an actual decision. For the broader landscape see our best ISA platforms UK 2026 comparison which puts both against the flat-fee alternatives.

This article is for informational purposes only and does not constitute financial advice. You should seek independent financial advice before making any investment decisions.