A rupee is not the only money
An overseas agent invoiced in dollars, an OTA remitting in dollars: the invoice keeps its rupee value, carries a foreign face at the rate it was quoted, and at month end the open balance is revalued with the gain or loss named in the books.
Every hotel here keeps its books in rupees and every card is settled in rupees. Where a foreign currency actually reaches a hotel is the city ledger — the overseas travel agent, the OTA that remits in dollars. The invoice is booked at today's rate, the money comes at another, and the difference is a gain or a loss the books must name.
Rates and faces
A dated rate per currency — spot, monthly or manual, with its source; the rate in force on a date is the latest on or before it. An invoice or a vendor bill keeps its rupee gross and gains a foreign face beside it: the gross divided by the rate the customer was quoted. Nothing on the invoice is edited.
The month-end mark
Every open foreign receivable and payable is valued at the day's rate and compared with the rupees it is carried at. The movement since the last mark is posted, so the balance sheet shows the receivable at today's rate and the profit and loss takes only the change; a re-run on the same rate moves nothing. When a foreign invoice is settled its last mark is the realised gain or loss. The exposure and every revaluation run are reports.
Not yet
A gain or loss split inside a receipt; foreign-currency bank accounts; a foreign folio — the guest's bill is rupees, and the gateway settles cards in rupees; a reporting currency for the group. Each waits for a customer who needs it.