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The short answer
For a UK resident, the ISA is the simplest tax shelter available: up to £20,000 a year (2026 to 2027) with no UK tax on interest, dividends or gains inside it. Nigerian investments can pay much higher nominal rates, but the income is normally taxable in the UK and the return in pounds depends on the naira. Many Nigerian savers in the UK fill the ISA with long-term money first and put into Nigeria only what they plan to spend there or can afford to see fall in sterling terms.
What the ISA gives you
GOV.UK sets the ISA allowance for 2026 to 2027 at £20,000. You can split it across cash, stocks and shares, innovative finance and Lifetime ISAs. You must be 18 or over (18 to 39 to open a Lifetime ISA) and UK resident, or a Crown servant or member of the armed forces abroad, or their spouse. ISAs cannot be held jointly.
The point is the tax. GOV.UK lists ISAs among the things outside Capital Gains Tax, and interest and dividends inside an ISA are not taxed. Outside an ISA, the 2026 to 2027 dividend allowance is £500, with dividend tax at 10.75%, 35.75% or 39.35% depending on your band, and the Capital Gains Tax annual exempt amount is £3,000, with rates of 18% and 24%.
What Nigerian investments give you
Naira rates are much higher on paper. As at October 2026, Nairametrics reported Treasury bill stop rates of 15.50% (91 days) to 15.85% (364 days) at the 7 October 2026 auction, and FGN Savings Bond rates of 13.071% (two years) and 14.071% (three years) for the October offer. Against that, three costs apply to a UK resident:
- Nigerian tax at source on some instruments. A November 2025 Mondaq summary reports a FIRS directive (dated 16 September 2025) requiring 10% withholding tax on interest from short-term securities, including Treasury bills. The DMO says its savings bonds are not taxed in Nigeria.
- UK tax. GOV.UK says UK residents normally pay UK tax on foreign income, including interest, usually through Self Assessment. The UK–Nigeria treaty gives credit for Nigerian tax paid, but you pay the difference up to your UK rate.
- Currency. You convert pounds into naira and later back, paying a margin each way, and your return in pounds depends on how the naira moves.
A worked example
Labelled example, rounded, ignoring conversion margins. Funmi is a higher-rate taxpayer with £5,000 to invest for one year.
| Cash ISA at an example 4% | Naira T-bill at an example 15% | |
|---|---|---|
| Interest before tax | £200 | Equivalent of £750 in naira |
| Nigerian withholding tax (10%) | None | £75 |
| UK tax at 40%, less credit for Nigerian tax | None | £300 − £75 = £225 |
| Net interest | £200 | £450 before currency move |
| Naira falls 10% against the pound | No effect | Whole £5,450 shrinks to about £4,905 |
| Result in pounds | £5,200 | About £4,905 |
In this example everything in naira, including the tax lines, scales down with the currency, so a 10% fall in the naira turns a higher naira rate into a loss in pounds. If the naira had held steady, the naira bill would have come out ahead, at £5,450. The ISA result is known in advance; the naira result depends on a currency move nobody can predict. Your own figures will differ, and this is information, not advice.
When putting money into Nigeria first makes sense
- You will spend the money in naira. School fees, building costs, support for parents. Holding naira for naira bills removes the currency risk on that money.
- You are leaving the UK. GOV.UK says you must be UK resident to pay into an ISA; for what happens to one you already hold, see what happens to your ISA if you leave the UK.
- You have already used this year’s allowance. Then the comparison is between Nigerian assets and taxable UK ones, not the ISA.
Can you hold Nigerian assets inside an ISA?
GOV.UK says a stocks and shares ISA can hold shares, unit trusts and funds, but each ISA manager decides which investments it offers. Some UK platforms may offer funds with exposure to Nigeria or frontier markets; shares you already hold through a Nigerian broker sit outside any UK ISA. See stocks and shares ISAs for Nigerians in the UK and UK ISA or naira savings.
What to check first
- How much of this year’s ISA allowance you have already used, across all your ISA accounts.
- Your UK tax band, because it decides how much UK tax you pay on naira interest.
- The conversion cost each way between pounds and naira, shown before you approve.
- When you will need the money, and in which currency.
A sensible order
- Keep an emergency fund in sterling.
- Use the ISA for long-term UK savings and investments.
- Hold naira for planned naira spending.
- Treat anything beyond that in Nigeria as a currency-exposed investment, sized so a large naira fall would not hurt your UK life.
Where Pryme fits
Pryme is not an ISA provider. For the naira side of your plan, a Pryme account holds pounds and naira side by side, converts only when you choose with the rate and fee shown first, and offers naira Savings Boxes for money held in Nigeria, with rates shown in the app.
Questions people ask
Should I max out my ISA before investing in Nigeria?
Many UK residents do, because ISA returns are free of UK tax and in pounds. Naira investments are taxable in the UK and exposed to the exchange rate.
What is the ISA allowance for 2026/27?
£20,000, according to GOV.UK, split across ISA types as you choose.
Are Nigerian T-bills tax free for UK residents?
No. Nigeria deducts 10% withholding tax on T-bill interest under a 2025 directive, and the UK normally taxes the interest as foreign income, with credit for the Nigerian tax.
Can I put Nigerian shares in my ISA?
Shares held through a Nigerian broker sit outside a UK ISA. Your ISA manager decides what it offers, and some platforms may have funds with Nigerian or frontier exposure.
Sources
- GOV.UK: Individual Savings Accounts (updated 30 Sep 2026) · accessed Oct 2026
- GOV.UK: Tax on dividends (updated 30 Sep 2026) · accessed Oct 2026
- GOV.UK: Capital Gains Tax rates and allowances (updated 2 Oct 2026) · accessed Oct 2026
- GOV.UK: Tax on foreign income · accessed Oct 2026
- Mondaq (Advocaat Law Practice): FIRS imposes 10% withholding tax on interest on short-term securities, 14 Nov 2025 · accessed Oct 2026
- Nairametrics: DMO raises N968.47 billion as 364-day stop rate falls to 15.85%, 7 Oct 2026 · accessed Oct 2026
This article is general information, not financial, legal or tax advice. Products described are provided under the terms on this site and are subject to regulation and eligibility.