What £300 a Month into an ISA Could Look Like Over 20 Years
There's something oddly satisfying about running the numbers on long-term investing. You plug in a monthly amount, pick a timeframe, and watch the projections stack up. It doesn't tell you what will happen - markets don't work that way - but it does give you a sense of what's possible under different scenarios.
If you've ever wondered what putting £300 a month into an ISA might look like over 20 years, this article walks through an illustrative example using the projection rates regulators ask platforms to show.
This is educational only. We're not making forecasts or recommendations - just showing how these scenarios are typically constructed.
The scenario we're exploring
To keep this simple, we're using:
- Monthly contribution: £300
- Time horizon: 20 years (240 months)
- Total contributions: £72,000 (£300 × 240 months)
- Growth rates: FCA standard projection rates of 2%, 5%, and 8% per year
These rates aren't predictions. They're standardised figures used across the industry to help people compare how different growth assumptions might affect long-term outcomes.
Source:
FCA Handbook – COBS 13 projection rates.
What the numbers could illustrate
Here's what the scenario might show at the end of 20 years, based on the three FCA projection rates:
A few things stand out:
- At 2%, the illustration shows modest growth above the total contributions
- At 5%, the illustrated growth begins to exceed the amount contributed
- At 8%, the projected growth represents a significant portion of the end value
None of these outcomes are guaranteed. Markets fluctuate. Returns vary year to year. But this is how these projections are typically shown.
How tax-free treatment affects these illustrations
One thing worth noting: all of the illustrated growth in these scenarios would be sheltered from UK income tax and capital gains tax if held within an ISA.
HMRC confirms that investment returns inside an ISA are exempt from these taxes. This means:
- Dividends earned are not subject to dividend tax
- Capital gains are not subject to capital gains tax (CGT)
- Withdrawals are tax-free
If the same investments were held outside an ISA, a portion of the returns might be taxed each year (depending on individual circumstances and allowances). Over 20 years, this "tax drag" could affect the end result, though the exact impact would depend on tax rates and personal allowances at the time.
Tax treatment depends on individual circumstances and may change.
Source: HMRC – Capital gains tax allowances
Why this matters for halal investors
Muslim investors who avoid interest (riba) often have fewer options for conventional savings products. This can make tax-efficient investing particularly relevant.
Here's how it connects:
- The ISA itself is neutral - it's just a tax wrapper. Whether it's permissible under Islamic principles depends entirely on what's held inside it.
- A Cash ISA at a conventional bank typically pays interest, which is not permissible. A Cash ISA at an Islamic bank may be structured using profit-sharing contracts, which could be considered permissible depending on the structure.
- A Stocks & Shares ISA can hold Shariah-compliant assets such as screened equities, Sukuk, or gold - provided the underlying investments meet Islamic finance criteria.
When interest-based products are not an option, the tax advantages of a halal Stocks & Shares ISA can become more meaningful. It allows for potential growth without riba and without the erosion of returns through annual taxation.
Platforms that specialise in Shariah-compliant investing, such as Wahed, offer screened portfolios within a Stocks & Shares ISA structure. This may simplify the process for those seeking permissible investment options within a tax-efficient wrapper.
Explore your own scenarios
The £300/month example is just one illustration. Your own circumstances, contribution level, and timeline may be different.
To explore scenarios based on your own inputs - such as different monthly amounts, timeframes, or growth assumptions - you can use an ISA scenario explorer tool. These tools allow you to adjust the variables and see how the projections change under different conditions.
[Explore ISA Scenarios] (Link to tool)
Remember: these are illustrations only. They are not forecasts, and actual outcomes will depend on market performance, the assets held, fees, and individual circumstances.
Final thoughts
Illustrative scenarios like this can be useful for understanding how regular contributions and compound growth might interact over time. They don't predict the future, but they can provide a framework for thinking about long-term saving and investing.
If you're considering an ISA - particularly a Shariah-compliant one - understanding the mechanics of tax-free growth, Shariah screening, and the difference between savings and investment products may help inform your approach.
Risk Warning: Equity investments are not readily realisable and involve risks, including loss of capital, illiquidity, lack of dividends and dilution, and it should be done only as part of a diversified portfolio. Investments of this type are only for investors who understand these risks. You will only be able to invest in the company once you have met our conditions for becoming a registered member.
Please visit www.wahed.com/uk/ventures/risk for our full risk warning.
Risk Warning: As with any investment, a Wahed Invest Ltd investment puts your money at risk, as the value of your investment can go down as well as up. The tax treatment of your investment will depend on your individual circumstances and may change in the future. If you are unsure about whether investing is right for you, please seek expert financial advice.
Please visit www.wahed.com for our full terms and conditions
Maydan Capital Limited, trading as WahedX, is registered in England and Wales (Company No. 13451691), registered office: 87-89 Baker Street, London, W1U 6RJ, UK. Maydan Capital Ltd (FRN: 963613) is an appointed representative of Wahed Invest Ltd (FRN: 833225), an authorised and regulated firm by the Financial Conduct Authority.Wahed Invest Ltd. is registered in England and Wales (Company No. 10829012), registered office: 87-89 Baker Street, London, W1U 6RJ, UK and is authorised and regulated by the Financial Conduct Authority: FRN 833225.
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As with any investment, a Wahed Invest Ltd investment puts your money at risk, as the value of your investment can go down as well as up. The tax treatment of your investment will depend on your individual circumstances and may change in the future. If you are unsure about whether investing is right for you, please seek expert financial advice.
Wahed Invest LLC (Wahed) is a US Securities and Exchange Commission (SEC) registered investment advisor. Wahed Invest provides brokerage services to its clients through its brokerage partner Apex Clearing Corporation, a member of NYSE - FINRA - SIPC and regulated by the SEC and the Commodity Futures Trading Commission. Registration does not imply a certain level of skill or training. Wahed does not intend to offer or solicit anyone to buy or sell securities in jurisdictions where Wahed is not registered or a region where an investment practice like this would be contrary to the laws or regulations. Any returns generated in the past do not guarantee future returns. All securities involve some risk and may result in loss. Any performance displayed in the advertisements or graphics on this site are for illustrative performances only.
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