如何计算ISA

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An ISA (Individual Savings Account) is a tax-free wrapper for savings and investments. Any growth, interest, or dividends earned within an ISA are completely free from Income Tax and Capital Gains Tax — forever. The annual allowance is £20,000 per person (2024/25). Unused allowance cannot be carried forward.

公式

Compound growth formula: FV = PV × (1+r)^n + PMT × ((1+r)^n − 1)/r

FV: PV × (1+r)^n + PMT × ((1+r)^n − 1)/r — PV × (1+r)^n + PMT × ((1+r)^n − 1)/r
PV: PV value — Variable used in the calculation
PMT: PMT value — Variable used in the calculation

分步指南

1Contribute up to £20,000 per tax year (April 6 – April 5)
2Stocks and Shares ISA: invest in funds, shares, ETFs — suitable for 5+ year horizons
3Cash ISA: earn interest tax-free — better than regular savings account for higher-rate taxpayers
4Lifetime ISA (LISA): 25% government bonus on up to £4,000/year — for first home or retirement
5Compound growth formula: FV = PV × (1+r)^n + PMT × ((1+r)^n − 1)/r

例题解析

输入

£500/month for 20 years at 7% return

结果

~£248,000 projected

£120,000 contributed, £128,000 tax-free growth

输入

£20,000 lump sum for 30 years at 7%

结果

~£152,000

All gains completely tax-free

常见问题

What is Isa?

How accurate is the Isa calculator?

The calculator uses the standard published formula for isa. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

What units does the Isa calculator use?

This calculator works with inches, British pounds, percentages. You can enter values in the units shown — the calculator handles all conversions internally.

What formula does the Isa calculator use?

The calculator applies the standard formula for this type of calculation. See the 'How It Works' steps above for the detailed formula breakdown.

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