Invoice currency and exchange-rate control: preserve the source and the conversion

Currency control begins by preserving what the supplier actually invoiced. Record the invoice currency, each line and document total in that currency, the date fields, and any supplier-stated rate or tax amount. Only then apply the restaurant’s approved conversion policy. A payment may use a different bank rate from the accounting rate; a credit note may arrive later; and rounding at line level can differ from rounding at document level. Those are reconciliation questions, not reasons to overwrite the source. Keep a clear bridge from source amount to converted amount and identify who can approve a departure.

Choose and document the conversion basis

The policy should define the rate source and the relevant date or event for each transaction type. It may distinguish a purchase invoice, receipt, credit note, payment, deposit, or period-end balance. Do not copy a rate from a search result, supplier email, or memory without recording its source and applicability. Show whether the formula multiplies or divides, and keep enough decimal precision during the calculation to reproduce the result before applying the documented rounding rule. If a local tax rule requires a different basis from the accounting conversion, store both decisions with their sources. Current national requirements and adviser review control the final treatment.

• Store the original displayed amount and currency before translating labels, separators, decimal marks, or symbols.
• Record rate source, retrieval or effective date, direction, precision, formula, and rounding method in the conversion evidence.
• Keep invoice, order, accepted receipt, credit, payment, and ledger references together when currency differences can affect matching.
• Flag a rate unavailable, stale, contradictory, or manually overridden instead of substituting an unrecorded number.
• Restrict edits after posting and retain the prior calculation, reviewer, and reason when a correction is required.

Reconcile rounding, tax, and settlement differences

A small difference can arise from line rounding, document rounding, tax calculation, bank settlement, fees, or a rate applied on a different date. First identify the source and stage. Compare source-currency commercial values, the conversion formula, intermediate precision, rounded lines, tax fields, document total, payment evidence, and ledger value. Do not label every residual as an exchange gain or loss, recoverable tax, supplier error, or immaterial amount without the policy and jurisdiction-specific review that supports that classification. When an operator enters an override, require a reason and approval and keep the unadjusted calculation available for comparison.

Clearly labeled illustrative example: one foreign-currency invoice

A repeatable invoice currency-control process

1. 1Capture source values. Save invoice currency code, displayed amounts, lines, dates, tax fields, supplier rate, references, and the original document before conversion.
2. 2Select approved basis. Apply the local policy’s rate source, relevant date or event, conversion direction, precision, and rounding rule and record the evidence.
3. 3Calculate the bridge. Show source amount, formula, intermediate result, line or document rounding, converted amount, and any operator-entered override separately.
4. 4Match the transaction. Compare source and converted values with order, accepted receipt, credit, payment, ledger, and tax records and classify residual differences.
5. 5Review exceptions. Have an authorised reviewer assess stale or missing rates, overrides, fees, rounding, period, and jurisdiction-specific tax or accounting questions.
6. 6Post and preserve. Record the approved result, keep source and calculation evidence, restrict later edits, and link corrections without deleting the prior version.