For a one-time expense on a specific date, the IRS's general rule is to use the spot rate prevailing when the amount is paid, not a yearly-average table meant for income received evenly across a year; the IRS states it has no official exchange rate and generally accepts any posted exchange rate used consistently. GBP500 spent on a single day at a posted spot rate of 1.2680 USD per GBP1 converts to $634.00.
What spot rate single date foreign expense means
The IRS's own currency-exchange guidance states, 'In general, use the exchange rate prevailing (i.e., the spot rate) when you receive, pay or accrue the item,' and separately states that the Service has no official exchange rate and generally accepts any posted exchange rate that is used consistently, such as a rate from a bank or another verifiable source. This differs from the yearly-average approach this site's own IRS guide covers, which the IRS itself limits to income received evenly throughout the year; a single dated expense, like one hotel night or one client dinner paid abroad, is a specific-date transaction the general spot-rate rule governs instead, not the averaged shortcut.
| Expense | GBP500 hotel stay, one date |
|---|---|
| Posted spot rate for that date | 1.2680 USD per GBP1 |
| Correct spot-rate conversion | $634.00 |
| If yearly-average table misapplied | about $658.76 |
| Difference from misapplying the wrong table | about $24.76 |
What exchange rate should you use to convert a single foreign business expense?: worked example
An employee pays GBP500 for a hotel stay on a specific business-trip date. Using a posted spot rate for that date of 1.2680 USD per GBP1, the reimbursable dollar amount is 500 times 1.2680, or $634.00. If the same GBP500 were instead run through the IRS's separate yearly-average table for that tax year, at an illustrative 0.759 GBP per USD1, the result would be 500 divided by 0.759, or about $658.76, roughly $24.76 higher than the correct spot-rate figure, because the yearly-average table answers a different question than a single dated expense requires.
How to calculate spot rate single date foreign expense
Identify the exact date the expense was paid, then find a verifiable posted exchange rate for that date from a consistent source, such as a bank, the Federal Reserve's H.10 release, or another reputable provider. Reimbursable amount = foreign-currency amount times the spot rate for that date. Record the source and the date alongside the converted figure, since the IRS's acceptance of the rate depends on consistent use, not on which specific reputable source was chosen.
Use the relevant inputs with these related Calculatort pages: currency conversion tool · IRS yearly-average rate guide · historical exchange-rate guide.
Common mistakes
Do not default to the IRS yearly-average table for a single dated expense, since that table is meant for income spread evenly across the year, switch rate sources between similar expenses to get a more favorable dollar figure, which the IRS's consistency requirement does not allow, or use a rate from a date near, but not matching, the actual date of payment without documenting why the exact date's rate was unavailable.
Where this calculation stops
This describes the general spot-rate rule and the IRS's source flexibility for a single transaction; it does not determine whether the underlying expense is deductible or reimbursable under a specific policy, does not apply to income meant to be translated under the yearly-average shortcut, and does not replace a tax professional's review of a specific expense report or return.
A second expense, a different currency and a smaller amount
A JPY22,000 taxi and meal expense on a separate single date, converted at an illustrative posted spot rate of 0.00658 USD per JPY1 for that date, comes to 22,000 times 0.00658, or $144.76. As with the GBP example, the correct approach looks up a verifiable rate for that specific date rather than reaching for a yearly-average figure meant for a different kind of income entirely, and the same consistency requirement applies regardless of which currency or how small the amount is.
Checking the GBP500 conversion by reversing it
To verify $634.00, divide it back by the same 1.2680 spot rate: 634.00 divided by 1.2680 returns exactly 500.00, confirming the rate and amount were carried through correctly. A reverse check that does not return the original GBP500 signals either a transcription error in the posted rate or that the wrong rate, such as the yearly-average figure from the comparison above, was used in place of the intended spot rate.
Picking among several verifiable posted-rate sources for the same date
| Source type | What it offers for a single date |
|---|---|
| A bank's own posted rate | the rate that specific institution would have applied that day |
| Federal Reserve H.10 release | a weekly-published, dated noon buying rate for major currencies |
| A reputable rate-data provider | a daily historical rate lookup for a wide range of currencies |
The IRS does not require any one of these over another; it requires that whichever source is chosen be reasonably verifiable and applied consistently across similar expenses, not swapped from expense to expense to reach a more favorable dollar figure.
What changes if the exact payment date's rate is not available from any source
A currency pair or a specific date can sometimes be missing from a chosen source, such as the Federal Reserve's H.10 release covering only a defined list of major currencies on business days only, as this site's own H.10 guide describes. When the exact date is unavailable, the closest published business-day rate from the same source, clearly documented as a substitution and applied the same way to comparable expenses, keeps the record consistent; switching to a completely different source only for the missing date reintroduces the cross-source comparability problem this guide's core example is built to avoid.
The dispute this guide resolves: 'the IRS requires OANDA' or a specific vendor
A common misunderstanding is that the IRS requires a rate from one specific commercial data vendor for a single-date foreign expense. The IRS's own language names no required vendor; it accepts any posted, verifiable, consistently used rate, whether from a bank, a government release such as the Federal Reserve's H.10 series, or a commercial historical-rate lookup service. What the IRS does require is that the chosen source and method not be switched between comparable transactions to produce a more favorable result, which is a consistency rule about the taxpayer's own practice, not an endorsement of any single named provider.
Documenting the source alongside the number, not just the number
Because the IRS's acceptance of a posted rate depends on consistent use rather than on any single mandated figure, an expense report or return that only records the converted dollar amount, without noting which source and date produced the underlying rate, leaves nothing to demonstrate consistency if a later expense uses a different source. Recording the source name, the exact date, and the rate itself alongside the converted figure, the same three-part record this site's own historical-rate guide recommends for a Federal Reserve H.10 lookup, turns a single defensible conversion into a pattern that can be shown to be consistent across an entire expense report or tax year.
Source and verification
The IRS states that in general, taxpayers should use the exchange rate prevailing, meaning the spot rate, when an item is received, paid, or accrued, and separately states that it has no official exchange rate and generally accepts any posted exchange rate that is used consistently. Read the named source. Verify the source date and the controlling statement, agreement, payroll record, or accounting record before relying on the illustrated result.