The actual minimum
Most UK investment platforms let you start with £1. Trading 212 has no minimum. Vanguard Investor requires £100 to open but accepts £1 after that. InvestEngine starts at £1. The practical question isn't what the platform allows, it's what makes sense for you. Most beginners find £25–£50 a month is a meaningful starting point.
The better question is what you can commit to every month without stopping when life gets difficult.
What to sort out before you invest
Two things take priority over a Stocks and Shares ISA: high-interest debt and an emergency fund. Credit card debt at 20% APR is a guaranteed 20% return to pay it off, no investment reliably beats that. Workplace pension matched contributions are the exception: if your employer matches 5% with their own 5%, that's an immediate 100% return. Always contribute enough to get the full match.
The emergency fund rule
Before investing anything beyond your workplace pension, build a cash buffer of 3–6 months of essential expenses in an easy-access savings account. Investments go up and down. If a boiler breaks while your money is invested and the market is down, you either sell at the wrong moment or go into debt. The emergency fund stops that from happening.
Working out a monthly amount
Start with your take-home pay. Subtract essential fixed costs: rent, bills, food, transport. What's left is discretionary income. From that, decide what goes to investing. The 50/30/20 rule (50% needs, 30% wants, 20% savings and investing) is a reasonable reference point for average earners, but it breaks down for people in high-cost cities or on lower incomes.
We started with £200 a month. When the redundancy hit we dropped to zero for two months, then restarted at £150. The habit of a regular amount, automated, is more important than the specific number.
Why consistency beats amount
Investing £50 a month for 10 years outperforms investing £500 a month for 2 years, all else being equal. Time in the market is the most powerful factor in long-term returns, and consistency is what keeps you in the market. Set up a direct debit for the day after your salary lands. Make it automatic. Remove the monthly decision entirely.
When to increase contributions
Review the amount when your financial situation changes, a pay rise, a debt cleared, an expense that disappears. One useful habit: when you get a pay rise, direct half the after-tax increase into investments and keep half as lifestyle improvement. The increase in contributions doesn't feel like a sacrifice. Want help thinking through the ISA vs savings decision? Our guide on ISAs vs savings accounts explains when each makes sense.
Module 2 covers emergency funds, debt, and budgeting, so you know exactly what you can comfortably invest before you start. Three modules free.
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