AI agents for business finance: what they can and can't do
What AI agents can do in bookkeeping, close, collections and compliance today, where a person must stay in charge, and how to judge a product.
The short answer
Yes, exchange movements can create or remove a taxable gain, because the UK, US and Canada measure gains on Nigerian assets in their own currency. HMRC converts the cost at the rate on the day you bought and the proceeds at the rate on the day you sold; CRA does the same. Since the naira has fallen sharply against major currencies, a large naira profit can turn into a gain, a smaller gain or even a loss in pounds or dollars, and naira cash itself has its own rules.
The basic rule: convert at each date
HMRC's Capital Gains Manual (CG78310) says that for an asset bought and sold in a foreign currency, the cost is the sterling value at the date of acquisition and the proceeds are the sterling value at the date of disposal. You do not work out the naira gain and then convert it. CRA's capital gains guide (T4037) gives the same method for Canadian residents: proceeds at the exchange rate at the time of sale, the cost base at the rate when the property was acquired, and expenses at the rate when they were incurred. The IRS asks US taxpayers to report in dollars using the rate prevailing when each item is received, paid or accrued.
The result is that the currency movement is built into the gain. Nobody taxes the naira profit as such; they tax the change in value in their own currency.
Worked example: a Lagos flat
Example only; the rates are illustrative, not historical. Ada, resident in the UK, bought a flat for ₦50,000,000 when £1 bought ₦500, and sold it for ₦120,000,000 when £1 bought ₦2,000.
| Naira | Rate | Sterling | |
|---|---|---|---|
| Cost | ₦50,000,000 | ₦500 = £1 | £100,000 |
| Proceeds | ₦120,000,000 | ₦2,000 = £1 | £60,000 |
| Result | ₦70,000,000 gain | £40,000 loss |
In Nigeria Ada has a ₦70,000,000 gain; under the Nigeria Tax Act 2025, Bloomberg Tax explains, an individual's chargeable gains are added to income and taxed at personal income tax rates, with no indexation. In the UK she has a £40,000 loss. Had she sold for ₦250,000,000 at the same rate, her sterling proceeds would be £125,000 and she would have a £25,000 UK gain, smaller than the naira figure suggests. For what to do with the loss, see claiming a currency loss.
Naira cash and bank balances
Currency itself is treated differently in each country.
- UK. CG78300 says currency other than sterling is a chargeable asset. But from 6 April 2012 an individual's foreign currency bank account is treated as a simple debt, so no chargeable gain or loss arises for the original holder (CG78320, as summarised in HMRC's manual). Currency acquired for personal expenditure outside the UK, including a residence abroad, is also exempt.
- US. Section 988(e) of the Internal Revenue Code treats personal transactions of individuals separately: on disposing of foreign currency in a personal transaction, no gain is recognised unless it exceeds $200. Transactions connected to investment fall outside the personal exception.
- Canada. T4037 says gains or losses from foreign currency capital transactions are reported only to the extent the net gain or loss for the year exceeds $200.
Because the naira has mostly fallen, naira cash usually produces losses rather than gains for someone abroad. A gain arises in the other direction, for example if you hold dollars that you convert into naira after the dollar has risen against your home currency.
Shares, bonds and T-bills
The same conversion method applies to NGX shares and naira bonds sold before maturity: cost at the purchase-date rate, proceeds at the sale-date rate. Income such as dividends or T-bill discount is converted at the rate when received. See declaring gains on Nigerian shares and T-bill income abroad.
Which exchange rate
HMRC accepts any reasonable and consistent rate source for capital gains (CG78310 refers to the cases on this point). The IRS has no official rate and accepts posted rates used consistently. CRA uses Bank of Canada rates, where available. Whatever you use, record the source and keep to it; see choosing an exchange rate.
What to keep
- Purchase documents with the date and naira price.
- The exchange rate on the purchase date and its source.
- Invoices for improvements, with dates.
- Sale documents with date, price and costs.
- The rate on the sale date.
The Nigerian tax on the same sale
Nigeria looks only at the naira figures. Bloomberg Tax's summary of the Nigeria Tax Act 2025 says an individual's chargeable gain is added to total income and taxed at personal income tax rates, with the first ₦800,000 of total income exempt and a top marginal rate of 25%. The gain is proceeds less acquisition cost, enhancement spending and incidental costs such as legal, valuation and brokerage fees and stamp duty; there is no indexation for inflation. A one-time exemption applies to a principal private residence.
This creates an awkward mismatch. In Ada's example Nigeria may tax a ₦70,000,000 gain while the UK sees a £40,000 loss. With no UK tax on the sale, there is nothing for the Nigerian tax to be credited against, so it becomes a final cost. Knowing this before a sale helps with timing and with deciding whether to sell at all. See CGT when selling property from abroad.
Where Pryme fits
A Pryme multicurrency account keeps NGN, USD, GBP and EUR separately, so money stays in the currency it arrived in until you choose to convert with Swap. Each Swap shows the rate and the fee before you approve and leaves a dated record, which is the evidence a currency calculation needs.
Questions people ask
Is a gain caused by exchange rates taxable?
In the UK, US and Canada gains are measured in the home currency, so exchange movements are part of the taxable gain or loss.
How does HMRC convert a naira property sale?
Cost at the sterling value on the purchase date, proceeds at the sterling value on the sale date, then the difference (CG78310).
Do I pay UK tax on gains in a naira bank account?
An individual's foreign currency bank account is treated as a simple debt from 6 April 2012, so no chargeable gain or loss arises for the original holder.
Is there a small exemption for currency gains in Canada?
Yes. Net foreign currency capital gains or losses of $200 or less in a year are not reported.
Sources
- HMRC Capital Gains Manual CG78310: computation of gains on foreign currency and assets · accessed Oct 2026
- HMRC Capital Gains Manual CG78300: foreign currency · accessed Oct 2026
- 26 U.S. Code § 988 (Cornell LII) · accessed Oct 2026
- CRA T4037 Capital gains · accessed Oct 2026
- Bloomberg Tax: New Nigeria tax law redefines capital gains tax for individuals · accessed Oct 2026
- IRS: Foreign currency and currency exchange rates · 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.