Making the most of your ISA allowance this tax year

ISAs remain one of the most popular ways to save tax-free. Whether you're adding to an existing ISA or thinking of opening your first one, it pays to understand the rules so you can make confident decisions. 

Maybe you're topping up an existing cash ISA. Or perhaps you're thinking about opening your first one. Either way, here's what you need to know about using your ISA allowance this tax year.

Understand the ISA allowance for 2025/2026

You can save up to £20,000 across all your ISAs in the 2025/2026 tax year. That might be in a cash ISA, stocks and shares ISA, Lifetime ISA, Innovative Finance ISA, or a mix; depending on your goals.

Key facts about ISAs

• The ISA allowance runs from April 6 to April 5.
• Any unused ISA allowance doesn't roll over to the next tax year. If you don't use it - you lose it.
• With Principality, you can pay into only one cash ISA each tax year. Other providers may allow multiple ISAs in the same year.
• Topping up over time (e.g. adding to your ISA each month) can reduce pressure to add a lump sum before the end of the tax year.

How to top up your cash ISA 

Topping up your cash ISA is usually pretty straightforward. Ways to add money to your cash ISA include:  

• Making a bank transfer from your current account.
• Setting up a standing order to save regularly.
• Making a one-off payment online or in branch. 

Before you top up, make sure you’re paying into the correct cash ISA account for this tax year. At Principality, you can only use your ISA allowance in one cash ISA per tax year. Other providers may allow you to split your allowance across multiple cash ISAs.

Check your ISA terms first

Not all cash ISAs accept top-ups, especially fixed rate ISAs. Some ISAs may have limits, minimum deposit requirements, or conditions for adding extra deposits.

Before you add more money to your ISA, double check:

• Does your ISA allow additional deposits?
• What's your remaining ISA allowance this tax year?
• Are there withdrawal penalties or notice periods?

Not sure? Check your account documents or contact your provider. A quick check now can help you make good decisions with your money later.

Why top up your ISA early? 

Adding money to your ISA sooner rather than later gives your money more time to earn interest; tax-free.

Here are some of the benefits of topping up your ISA early:

• Your money has more time to earn interest.
• You can spread out your contributions throughout the year.

Even small, regular top-ups can make a difference to your savings over time.

Quick reminder: Make sure your everyday bills and emergency fund are sorted before moving larger amounts of money into your ISA.

Your savings are protected

If your ISA provider is regulated by the FCA, your savings are protected by the Financial Services Compensation Scheme (FSCS). This covers eligible savings up to £85,000 per person, per provider.

If you have more than £85,000 in savings, consider spreading it across different providers to maximise your protection.

New to ISAs?

If you don't have a cash ISA yet, have a think about whether one is right for you. Check out our ISA basics guide or browse our cash ISAs to find out whether a cash ISA could suit your savings goals.