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
Record a naira invoice at the spot rate on the date of the transaction; an average rate for a week or month is acceptable only if rates did not move significantly. At each reporting date, retranslate unpaid naira balances at the closing rate and put the difference through profit and loss. If the naira trades at more than one rate, IAS 21 says to use the rate at which the cash could actually be settled.
The short rule
IAS 21, the international accounting standard on exchange rates (2026 text), gives a clear order, and Spanish practice follows the same logic, although your statutory accounts are prepared under Spain's own accounting rules:
| Moment | Rate to use | IAS 21 reference |
|---|---|---|
| Invoice issued or received | Spot rate on the transaction date | Paragraph 21 |
| Many small transactions | An average rate for the period, unless rates fluctuate significantly | Paragraph 22 |
| Period end, unpaid receivables and payables, bank balances | Closing rate | Paragraph 23 |
| Period end, non-monetary items at cost (stock, fixed assets) | Historical rate, no retranslation | Paragraph 23 |
| More than one rate available | The rate at which the cash flows could be settled | Paragraph 26 |
Exchange differences on settlement and on retranslation go to profit or loss in the period they arise (paragraph 28).
Choosing a rate source, and sticking to it
The standard tells you which date's rate to use, not which publisher. For a Spanish business invoicing in naira, the practical choices are:
- The rate your bank or provider actually applied to a conversion. Good for settlement entries, since it matches cash.
- A published reference rate, such as a central bank's official rate or a reputable market data source, for recording invoices. Check that it actually quotes the naira against the euro; where it does not, a documented cross rate via the US dollar is a common workaround.
- Your accounting software's feed, provided you know where it comes from and can print the history.
Whatever you choose, write it down in an accounting policy note, apply it consistently and keep the daily history. An auditor will forgive a reasonable source; they will question one that changes from month to month or that nobody can trace. We do not print a rate here because it moves daily; the rate your provider shows before you convert is the one that matters for settlement.
When the naira has more than one rate
You may find more than one naira rate quoted, for example an official rate and a market rate. IAS 21 deals with this directly. Where several rates exist, paragraph 26 requires the rate at which the future cash flows represented by the transaction could have been settled if they had occurred at the measurement date. If you could only ever obtain euros for your naira through a particular channel, that channel's rate is the relevant one. Where a currency is not exchangeable, or only an insignificant amount can be obtained, paragraphs 8B and 19A require an estimate of the spot rate that an orderly exchange would produce, with disclosures.
A year-end example
Illustrative rates, not real rates. On 10 December your SL invoices a Nigerian distributor ₦5,000,000 when your source shows ₦1,650 to €1, so you book €3,030.30. On 31 December the invoice is still unpaid and the closing rate is ₦1,720 to €1.
- Retranslate: ₦5,000,000 at ₦1,720 = €2,906.98.
- Book an unrealised exchange loss of €3,030.30 − €2,906.98 = €123.32 in the year's profit and loss.
- When the client pays in February, compare the euros actually received with €2,906.98 and book the further difference as a realised gain or loss.
The receivable has not changed in naira. Only its euro value has. That is why naira-denominated contracts carry real currency risk for a euro business, and why some Spanish firms invoice Nigerian clients in euros or dollars instead.
Tax returns use the same figures
Exchange differences in your accounts feed into the corporate tax return through the accounting result; your asesor will confirm whether any adjustment applies. VAT is a separate question: the euro value of an invoice for IVA purposes follows the IVA rules, and the Modelo 303 reports operations in euros; ask your asesor which rate they apply for IVA on foreign-currency invoices so the two do not drift apart. Our guide to Modelo 303 when you trade with Nigeria explains where those operations go.
Invoicing in euros instead
Some Spanish firms avoid the problem by invoicing Nigerian clients in euros. That moves the currency risk to the client, who must buy euros to pay, and it can slow payment or cost you the deal. If you do invoice in naira, consider shorter payment terms, a clause that adjusts the price if the rate moves beyond an agreed band, or a deposit on signature. None of these changes the accounting rules above; they change how much exchange difference you end up booking.
Where Pryme fits
On a Pryme Business Account, every conversion with Swap shows the rate and the fee before you approve, and both stay on the record, which gives you a traceable settlement rate for each naira receipt. For the ledger set-up, read keeping books in euros and naira; for statements an auditor can check, see verifiable receipts and statements.
Questions people ask
Which exchange rate do I use for a naira invoice in my Spanish accounts?
The spot rate on the transaction date, from a source you document and use consistently. An average rate for the period is acceptable only if rates did not fluctuate significantly (IAS 21 paragraphs 21-22).
Do I revalue unpaid naira invoices at year end?
Yes. Monetary items such as receivables are retranslated at the closing rate, with the difference in profit or loss (IAS 21 paragraphs 23 and 28).
What if the official and parallel naira rates differ?
IAS 21 paragraph 26 requires the rate at which the cash flows could actually be settled at the measurement date.
Can I use the rate my bank gave me?
For the settlement entry, yes: it matches the cash. For recording invoices, use a documented reference rate on the transaction date.
Sources
- IFRS Foundation: IAS 21 The Effects of Changes in Foreign Exchange Rates (2026 text) · accessed Oct 2026
- Agencia Tributaria: Modelo 303, instrucciones ejercicio 2026 (page updated 9 Jun 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.