UK Finance Guide — April 2026

Compound interest is the process by which interest is added to your balance and then earns interest itself. Over time this creates exponential growth — working powerfully for you when saving and powerfully against you when borrowing.

Simple vs Compound Interest

The Rule of 72

Divide 72 by your interest rate to estimate how long your money takes to double. At 4% AER your money doubles in approximately 18 years. At 7% it doubles in approximately 10 years.

Why Starting Early Matters

Compound Interest Working Against You

A £5,000 credit card balance at 24.9% APR paying only the minimum will take over 28 years to clear and cost more than £6,500 in interest — more than the original debt.

How to Make It Work For You

• Start saving and investing as early as possible — time is the biggest factor
• Use a Stocks and Shares ISA for compound growth completely tax-free
• Reinvest dividends rather than taking them as cash
• Maximise pension contributions — decades of compounding are transformative
• Eliminate high-interest debt urgently — compounding destroys wealth on the borrowing side

By Chandraketu Tripathi · Updated April 2026 · kaeltripton.com