Cash ISA limit 2027 planner

The calculator works out your cash ISA limit for 2026/27 and 2027/28 from your date of birth. In 2026/27 the whole £20,000 can go into cash ISAs. From 2027/28 the cash limit is £12,000, unless you're 65 or over on the last day of the tax year.

Your planned payments into stocks and shares, Lifetime and Innovative Finance ISAs are taken first. Cash gets what's left of the £20,000, up to the cash limit. What would have fitted in a cash ISA under the 2026/27 rules but doesn't under the new limit is the overflow.

For tax, the calculator assumes the overflow sits in cash outside an ISA, earning the interest rate you enter. It adds the overflow interest to the interest on the savings you already hold outside ISAs, takes off your personal savings allowance (£1,000 at the basic rate, £500 at the higher rate, nothing at the additional rate) and taxes the rest at your band's savings rate. The extra tax is the difference that the overflow makes.

Savings rates rise by two percentage points from 6 April 2027, to 22%, 42% and 47%. So the 2027/28 figure includes the rise on the interest you already pay tax on, shown separately.

What this calculator assumes

• The interest rate stays the same throughout, and interest is paid out rather than added to the balance.
• The 2027/28 savings rates and allowances carry on unchanged in later years. Nothing later has been announced.
• Your tax band doesn't change, and the starting rate for savings isn't used. It only helps people whose other income is below £17,570.
• The overflow stays outside ISAs, including after you turn 65. The table is an illustration, not a forecast.

The overall ISA allowance stays at £20,000 a year. What changes is how much of it can be cash. From 6 April 2027, anyone under 65 can pay up to £12,000 a year into cash ISAs. The remaining £8,000 can still go into stocks and shares ISAs, Innovative Finance ISAs or, up to £4,000, a Lifetime ISA.

The rules were set in the Individual Savings Account (Amendment) (No. 2) Regulations 2026, laid before Parliament on 14 September 2026. They also close the obvious routes around the limit:

• Under-65s can't transfer money from a stocks and shares or Innovative Finance ISA into a cash ISA.
• Interest paid on cash held inside a stocks and shares or Innovative Finance ISA is charged at a flat 22%. The provider pays it to HMRC; there's nothing to declare yourself.
• Money market funds held in a stocks and shares ISA have to meet a new requirement. Returns from shares, bonds and funds are not charged.

On the same date, the tax on savings interest outside ISAs rises by two percentage points at every band. The personal savings allowance and the £5,000 starting rate for savings stay as they are.

Savers aged 65 or over keep the whole £20,000 for cash ISAs. The test is your age on the last day of the tax year, so the full cash allowance applies for the whole tax year in which you turn 65.

For 2027/28, that means anyone born on or before 5 April 1963. Someone born on 6 April 1963 turns 65 on the first day of the next tax year, so their 2027/28 cash limit is £12,000 and their 2028/29 limit is £20,000.

2026/27 is the last tax year in which everyone can put the whole £20,000 into cash ISAs. Allowance left unused on 5 April is gone; it doesn't carry over. Many providers set their own cut-off a few days earlier, so a payment sent on the last day may not count for 2026/27.

The calculator shows what's left of your 2026/27 allowance from what you've paid in so far. The ISA allowance tracker breaks it down by type of ISA, including the Lifetime ISA's £4,000 limit.