Allowances and rules
How much you can put in, how the tax year works and what the main ISA rules say.
For information only, not financial advice.
The rules that apply to every ISA: how much you can pay in each tax year, how many ISAs you can have, what happens at the end of the tax year and what has been announced for later years. The figures themselves are on the ISA rules page, each with its gov.uk source and the date it was last checked.
Quick answers
How much can be paid into ISAs in a tax year?
For 2026/27 the overall ISA allowance is £20,000. It is the most that can be paid into ISAs in total in the tax year, however many ISAs are used and whichever types they are. The ISA rules page lists each limit with its gov.uk source.
Can unused allowance be carried forward?
gov.uk sets the allowance for each tax year and describes no carry forward, so an unused part is not added to a later year. The tax year runs from 6 April to 5 April.
Rules data last checked against gov.uk on 26 September 2026. For information only, not financial advice.
Tools for this topic
ISA Allowance Checker
See how much of this tax year's ISA allowance is left.
ISA Calculator
Estimate how a lump sum and monthly savings could grow, and see how much of this tax year's allowance is left.
Guides
- How Much Can I Put in an ISA Each Year? UK Limits Explained
The annual ISA allowance, how it is shared across ISA types, the Junior ISA limit and what happens if you pay in too much.
- How Does the Annual ISA Allowance Work?
How the annual ISA allowance works: what it covers, how it can be split across ISA types, and what gov.uk says about unused allowance.
- ISA Tax Year End: What Happens to Your Unused Allowance
When the ISA tax year ends, how the allowance is counted, what happens to an unused amount, and how transfers fit in. Based on gov.uk guidance.
- ISA Allowance for Couples: How It Works for Two People
ISAs cannot be held jointly; this site's own reading is one limit for each person. How that works for couples, and what happens when a spouse dies.
- How many ISAs can I have? UK rules explained
You can pay into more than one ISA of the same type in a tax year within the £20,000 allowance. Rules for Cash, Stocks and Shares, Lifetime and Junior ISAs.
- How Do You Open an ISA?
Who can open each type of ISA, what a provider asks for, how a transfer in differs from a new payment, and where gov.uk pages stay silent.
- What Are the Different Types of ISA in the UK?
The four adult ISA types (Cash, Stocks and Shares, Lifetime, Innovative Finance) and the Junior ISA: what each can hold and how withdrawals work.
- Upcoming ISA Changes: What Is Confirmed and What Is Only Proposed
A timeline of upcoming UK ISA changes, showing which are confirmed, which are announced with a start date and which are still only under consultation.
- Cash ISA changes from April 2027: £12,000 limit explained
Regulations made in 2026 set a £12,000 cash ISA limit from 6 April 2027, not yet in force, for savers under 65 at the end of the tax year. Who is exempt.
- Common ISA Mistakes and How the Rules Work to Avoid Them
Common ISA pitfalls, from withdrawing instead of transferring to going over the allowance, and what gov.uk says about each.
See also the ISA rules at a glance, the ISA glossary and all topics.