Topping up: raising your contributions as you earn more

The amount is the lever you control

You can't control what the market does next year. You can't reliably pick the best fund. But there's one input that's fully in your hands and has a bigger effect than almost anything else: how much you put in each month.

Once you've started investing, raising your monthly amount is the highest-impact thing you can do. Not switching funds. Not timing the market. Just topping up. Here's the maths.

£50 vs £100 a month: the real gap

Let's use a long-run assumption of 7% a year. This is an illustration to show how compounding works, not a guarantee. Real returns vary year to year, and some years are negative.

At £50 a month, invested steadily at 7% a year:

Years	You paid in	Illustrative value
10 years	£6,000	about £8,700
20 years	£12,000	about £26,200

Now double it to £100 a month, same 7% assumption:

Years	You paid in	Illustrative value
10 years	£12,000	about £17,400
20 years	£24,000	about £52,400

The point: doubling your monthly amount doesn't just double your paid-in total, it doubles the compounded result too. Over 20 years, that extra £50 a month turns into roughly £26,000 of extra value in this illustration. The sooner you raise the amount, the more years that money has to compound.

The invest-your-pay-rise trick

The hardest part of investing more is feeling the money leave. If you're already living on your current pay, moving from £50 to £100 a month can sting.

So don't take it from money you already spend. Take it from money you've never had. When your salary goes up, whether it's a pay rise, a new job, or the end of a loan, raise your standing order or auto-invest the same week, before the higher pay ever hits your everyday spending.

You never miss what you never budgeted for. A rise of £150 a month after tax? Send £50 or £75 of it straight to your ISA and keep the rest. Your day-to-day life doesn't change, but your monthly contribution just went up for good.

Some people set a simple rule: every time pay goes up, half of the increase goes to investing. You still feel richer each year, and your future self does far better.

Keep an eye on the £20,000 ISA allowance

Everything you invest inside a Stocks & Shares ISA grows free of UK capital gains and dividend tax. The catch is a yearly limit: you can pay in up to £20,000 per tax year, across all your ISAs combined.

For most people topping up, this is nothing to worry about. £100 a month is £1,200 a year, well under the cap. Even £500 a month is £6,000 a year. You'd need to be paying in more than £1,666 a month before the allowance comes into view.

If you ever do get close, that's a good problem to have. At that point you'd just direct the surplus to a General Investment Account alongside the ISA. But fill the ISA first, every year, because that allowance doesn't roll over. Use it or lose it.

How to actually change your monthly amount

On most UK platforms this takes about a minute. The wording differs, but the path is the same.

On Trading 212: open your Pie or your auto-invest settings, find the recurring order, and edit the amount. Confirm the new figure and the date it comes out. Done.

On InvestEngine: go to Savings Plan (or your recurring investment), change the monthly amount, and save. The next scheduled payment uses the new figure.

If you fund your investing with a monthly Direct Debit or standing order from your bank, remember to raise that too, so the cash is there to be invested. The two numbers should match: the amount leaving your bank and the amount being invested.

Set a reminder to review the figure once a year, ideally in April when the new tax year and any pay rise tend to land together. Small, regular top-ups beat one big effort you never get round to.

Next: keeping the mix right

Raising your contributions builds the pot faster. The next question is making sure that growing pot stays balanced the way you intended, so no single part quietly takes over. That's rebalancing, and it's where we go next.