The Wealth Wingwoman Audit
Audited by Valerie Vance"The showdown between InvestEngine and Interactive Investor (ii) represents the ultimate ideological divide in modern British wealth accumulation: an ultra-lean, automated ETF engine versus an established, flat-fee institutional supermarket owned by global asset manager abrdn. Both platforms are regulated by the Financial Conduct Authority (FCA) in the United Kingdom, protect eligible custodial assets and uninvested cash up to £85,000 under the Financial Services Compensation Scheme (FSCS), and provide core tax wrappers across Stocks & Shares ISAs, Self-Invested Personal Pensions (SIPPs), and General Investment Accounts (GIAs). Assuming they are direct competitors because both break away from traditional percentage-based custody fees is an expensive mistake. InvestEngine is an automated compounding machine built strictly around exchange-traded funds (ETFs): delivering £0 platform fees and £0 dealing commissions on DIY portfolios across ISAs, SIPPs, GIAs, and corporate Business Accounts—paired with fractional ETF shares down to pennies, automated portfolio rebalancing, and zero foreign exchange (FX) transaction drag. Interactive Investor is an institutional wealth titan operating on a flat monthly subscription (£5.99 on Core, £14.99 on Plus) that includes an ISA, SIPP, and GIA under a single price point—delivering whole-of-market access to over 40,000 instruments (including actively managed open-ended funds, UK Gilts, investment trusts, and direct US equities), pre-tax corporate employer pension contributions, native multi-currency USD accounts, and fee-free accounts for up to five family members."
The Tale of the Tape
InvestEngine was founded in 2019 to strip out the administrative overhead of traditional retail investing. It operates as an ETF-only execution and automation specialist. Rather than charging platform custody fees or dealing commissions on self-managed accounts, InvestEngine offers £0 DIY accounts across all retail wrappers. It provides access to over 600 exchange-traded funds across Vanguard, iShares, Invesco, and Xtrackers. It features fractional ETF investing, automated regular funding, one-click portfolio rebalancing, managed portfolios (at 0.25% p.a.), and corporate investment accounts for UK limited companies.
Interactive Investor (ii) is the UK’s primary flat-fee retail investment platform, supervising tens of billions in assets under abrdn. It operates on an all-inclusive subscription model: offering Core (£5.99/month for portfolios up to £100,000 across ISA, SIPP, and GIA) and Plus (£14.99/month for unlimited portfolio balances, covering an ISA, SIPP, GIA, and up to five family members). It provides comprehensive whole-of-market coverage across mutual funds (OEICs / unit trusts), exchange-traded funds (ETFs), individual equities, UK government bonds (Gilts), and corporate paper, supported by free monthly regular investing and telephone customer support.
The Fine Print Reality Check
Marketing teams pitch low costs, but long-term compounding in the UK is dictated by platform subscriptions, asset scope, pension contribution plumbing, multi-currency cash flows, and family wealth rails:
- The Platform Fee Equation (£0 vs. £71.88 to £179.88/Year): InvestEngine DIY charges £0 in annual platform fees, £0 in account custody fees, and £0 in dealing commissions across its ISA, SIPP, GIA, and Business Account. Whether you hold £10,000, £100,000, or £1,000,000 in exchange-traded assets, your platform holding cost is unconditionally zero. You pay only the underlying Ongoing Charges Figure (OCF) of the ETFs you hold. Interactive Investor operates on fixed monthly subscriptions: £5.99/month (£71.88/year) on the Core plan and £14.99/month (£179.88/year) on the Plus plan. If your portfolio consists entirely of low-cost broad-market index ETFs, holding them on Interactive Investor costs you £71.88 to £179.88 every single year in subscription overhead.
- The Asset Universe (600+ ETFs vs. 40,000+ Whole-of-Market Securities): InvestEngine is strictly an ETF platform. It offers 600+ exchange-traded funds. It has zero individual equities, zero unlisted mutual funds, zero investment trusts, and no direct UK Gilts. Interactive Investor provides whole-of-market access. It provides access to thousands of open-ended investment companies (OEICs) and unit trusts, investment trusts, UK Gilts and corporate bonds, primary retail bond offerings/IPOs, and individual UK and international equities.
- The SIPP Architecture (Institutional Flexibility vs. Lean Personal Rails): InvestEngine’s SIPP is a fee-free accumulation vehicle (£0 platform fee), but it supports personal contributions only. It does not accept employer pension contributions or limited company director payments. For retirement decumulation, drawdown is available on demand but relies on an offline, paper-based verification workflow through its trustee. Interactive Investor’s SIPP is a full-featured pension platform included inside its Core and Plus subscription plans. It accepts employer contributions, limited company director transfers, and third-party funding, and provides comprehensive retirement options including full digital Flexi-Access Drawdown.
- Corporate Treasury vs. Family Wealth Structuring: InvestEngine offers a dedicated Business Account for UK Limited Companies with £0 platform fees on DIY portfolios. For company directors holding retained corporate cash profits, InvestEngine lets you invest company reserves directly into diversified index ETFs. InvestEngine offers no Junior ISA (JISA). Interactive Investor (Plus Plan) includes its Family Plan: allowing you to add up to five family members with fee-free independent accounts covered under your single £14.99/month subscription. It also offers unlimited free Junior ISAs (JISAs).
- Foreign Currency Accounts vs. Zero-FX Execution: All available ETFs on InvestEngine are listed on the London Stock Exchange (LSE) and trade in GBP. InvestEngine charges 0% in foreign exchange fees. If you buy an S&P 500 ETF, your transaction executes in sterling with zero currency conversion drag. Interactive Investor provides a native multi-currency account. You can hold balances across 9 foreign currencies (including USD). US dividends settle directly into your USD cash balance. However, when currency conversions occur, ii charges 0.75% on Core, or 0.75% up to £50,000 and 0.25% thereafter on Plus.
- Automation & Fractional Compounding: InvestEngine supports fractional ETF shares down to penny increments. Its DIY Portfolios feature automated AutoInvest and one-click rebalancing without trading fees. Interactive Investor offers free automated monthly regular investing via Direct Debit, but discrete manual trades must be executed in full whole shares and incur dealing commissions (£3.99 for funds/shares on Core; £1.49 funds / £3.99 shares on Plus).
The Fine Print Translation
InvestEngine is an automated compounding machine built strictly around exchange-traded funds (ETFs): delivering £0 platform fees and £0 dealing commissions on DIY portfolios, paired with fractional ETF shares and one-click rebalancing. Interactive Investor is an institutional wealth titan operating on a flat monthly subscription (£5.99 to £14.99) that delivers whole-of-market access, corporate employer pension contributions, and fee-free accounts for up to five family members.
The Daily Driver Test
Your platform experience depends entirely on whether you prioritize automated, hands-off index allocation or full-spectrum portfolio governance.
InvestEngine operates like a precision portfolio-management terminal. The mobile app and web dashboard are clean, focused, and free of social distractions. Creating a portfolio takes minutes: you select your target asset allocation, set a weekly or monthly Direct Debit, and let the software work in the background. Because fractional ETF shares are supported down to the penny, every single pound you deposit is fully allocated immediately with zero cash drag. If market movements skew your asset split over time, clicking 'Rebalance' executes the required rebalancing orders across your portfolio with zero commission friction.
Interactive Investor operates like a professional investment dashboard. The desktop web portal and mobile app prioritize fundamental asset allocation: featuring comprehensive fund-selector screeners, Morningstar research ratings, macroeconomic commentary, and curated Super 60 and ACE 40 fund focus lists. For investors managing a holistic family balance sheet, managing your ISA, GIA, SIPP, and your children's JISAs from a single dashboard provides institutional clarity. Furthermore, if you need assistance with an estate transfer, probate, or complex pension rollover, calling ii connects you to an experienced UK telephone support team.
The Wingwoman Allocation
Don’t pay £180 a year in subscription fees just to hold broad-market index ETFs, and don’t trap your corporate pension in a broker that cannot accept employer contributions:
- Deploy with InvestEngine if: You invest exclusively in exchange-traded funds (ETFs) and want to secure £0 platform fees and £0 dealing commissions across your DIY ISA, SIPP, and GIA. You want automated, fractional portfolio compounding where automated rebalancing keeps your portfolio on target. You manage a UK Limited Company with surplus cash and want to open an InvestEngine Business Account to invest corporate reserves directly into ETFs at £0 platform cost.
- Deploy with Interactive Investor (ii) if: You hold unlisted mutual funds (OEICs) or individual shares: Buy actively managed funds, investment trusts, UK Gilts, or single US/UK stocks. You are a company director funding your pension: Use the ii SIPP to make direct, pre-tax employer pension contributions straight from your company bank account. You want to manage household wealth under one roof via the ii Family Plan. You require full pension decumulation: Access your retirement pot through automated Flexi-Access Drawdown with direct phone support.
Your Wingwoman Move
If your investment blueprint is built purely on compounding wealth through low-cost index-tracking ETFs, holding those assets on Interactive Investor generates unnecessary fee friction. Paying ii £71.88 to £179.88 every year in subscription fees for a passive ETF portfolio that InvestEngine custodies and executes for unconditionally £0 is an unforced drag on your net returns. InvestEngine eliminates platform fees, executes fractional shares down to pennies, rebalances your holdings with one click, and completely bypasses currency conversion fees by using LSE-listed instruments.
However, the moment your wealth strategy requires unlisted mutual funds (OEICs), individual equities, pre-tax corporate director pension contributions, full SIPP flexi-access drawdown, or multi-generational family accounts, InvestEngine hits a hard operational wall. Consolidate those balances into Interactive Investor: you cap your entire household's platform fees under a transparent flat subscription while unlocking the full depth of the UK financial market. Go get paid.