Understanding Savings Rates

AER, interest and what the numbers actually mean

TL;DR - Understanding Savings Rates 📋

  • AER is the best figure to compare savings accounts

  • It shows what you would earn over a year, including compounding

  • Gross rates and monthly interest can look higher than they really are

  • Bonus rates often drop after 6–12 months

  • Higher rates usually come with less flexibility

Why Rates Can Be Confusing 🤯

Savings adverts often show different figures — AER, gross interest, monthly interest, bonus rates — which makes comparison harder than it should be.

Understanding a few key terms will help you see past the marketing.

What is AER? 📈

AER stands for Annual Equivalent Rate.

It shows the interest you would earn over a full year, taking into account how often interest is added (compounded).

This is the most useful number when comparing accounts because it puts everything on a level playing field.

Gross Interest Rate 💷

"Ewww, gross!"

No, not that gross!

This is the interest rate before any tax (and before compounding is fully reflected).

It’s often the number that looks higher in adverts, but AER is still the better comparison tool.

How Compounding Works 🔁

When interest is added to your account, you then earn interest on the interest itself - this is "compounding".

The more frequently interest is paid (monthly vs annually), the more powerful this effect becomes — which is why AER is useful. It shows the true yearly return after compounding.

Bonus Rates 🎁

Many accounts offer a higher “bonus” rate for the first 6–12 months.

After the bonus period ends, the rate usually falls and sometimes significantly! Always check:

  • How long the bonus lasts

  • What the rate drops to afterwards

  • Whether you can easily move the money later

Variable vs Fixed Rates 🔄 vs 🔒

  • Variable rate – Can go up or down at any time. Most easy-access and notice accounts are variable.

  • Fixed rate – Stays the same for the whole term (common with fixed-rate bonds).

What Else Affects How Much You Earn?

These are some of the other factors that will affect how much you can earn

  • How often interest is paid (monthly interest can help compounding)

  • Whether you make withdrawals (some accounts reduce the rate if you withdraw)

  • Whether the rate is tiered (higher balances earn more — or sometimes less)

  • Tax (interest is taxable if you exceed your Personal Savings Allowance or don't save in an ISA)

Personal Savings Allowance (Quick Note) 🧾

Most people can earn some interest tax-free each year but it depends on your income tax band:

  • Basic-rate taxpayers: £1,000

  • Higher-rate taxpayers: £500

  • Additional-rate taxpayers: £0

Interest from Cash ISAs is always tax-free and does not use up this allowance.

Action Steps ✅

Now you have learnt what interest rates are and what the numbers actually mean, here's your homework:

  1. Always compare accounts using the AER.

  2. Check whether a high rate includes a temporary bonus.

  3. Note if the rate is variable or fixed.

  4. Look at how often interest is paid.

  5. Consider your tax position and whether a Cash ISA would be more efficient.

  6. Review your accounts when the bonus periods end or rates change.

Navigate all these acronyms and financial jargon, especially when confusing adverts bombard you with differing figures can be a challenge but you've now got a little more knowledge about what to look out for - you've got this!