A computer-implemented method for verifying authorisation of an electronic transaction in relation to a financial instrument of an originator of the electronic transaction, said method comprising the steps of: an originator computer system sending a request to a merchant computer system to process an electronic transaction for a predetermined amount of money; the merchant computer system forwarding the request to a verification agent computer system; receiving at the verification agent computer system a request to process an electronic transaction for a predetermined amount of money, said request comprising data identifying a particular financial instrument; the verification agent computer system dividing the predetermined amount into a plurality of charges, wherein the amounts of the plurality of charges are determined on a random basis; the verification agent computer system converting each of said plurality of charges to a respective charge ratio by dividing each of said plurality of charges by the predetermined amount, and storing each of said charge ratios; causing said financial instrument to be debited with each of said plurality of charges; the originator computer system checking the account relating to the financial instrument at an originator financial institution computer system and obtaining a number and individual amounts of the plurality of charges debited; the originator computer system advising the individual amounts of the plurality of charges to the merchant computer system and/or verification agent computer system; receiving at the verification agent computer system information relating to said plurality of charges from the originator of said request, the received information comprising a plurality of values relating to said plurality of charges debited to said financial instrument, wherein each of said values comprises one of the charges modified by a single currency exchange rate, the currency exchange rate being a factor of each value; converting by the verification agent computer system each of said received plurality of values to a respective value ratio by dividing by the verification agent computer system each of said plurality of values by the sum of said plurality of values; comparing by the verification agent computer system each of said value ratios to said stored charge ratios; and verifying by the verification agent computer system authorisation of said transaction only if each of said value ratios matches a respective stored charge ratio within a predefined margin of error. an originator computer system sending a request to a merchant computer system to process an electronic transaction for a predetermined amount of money; the merchant computer system forwarding the request to a verification agent computer system; receiving at the verification agent computer system a request to process an electronic transaction for a predetermined amount of money, said request comprising data identifying a particular financial instrument; the verification agent computer system dividing the predetermined amount into a plurality of charges, wherein the amounts of the plurality of charges are determined on a random basis; the verification agent computer system converting each of said plurality of charges to a respective charge ratio by dividing each of said plurality of charges by the predetermined amount, and storing each of said charge ratios; causing said financial instrument to be debited with each of said plurality of charges; the originator computer system checking the account relating to the financial instrument at an originator financial institution computer system and obtaining a number and individual amounts of the plurality of charges debited; the originator computer system advising the individual amounts of the plurality of charges to the merchant computer system and/or verification agent computer system; receiving at the verification agent computer system information relating to said plurality of charges from the originator of said request, the received information comprising a plurality of values relating to said plurality of charges debited to said financial instrument, wherein each of said values comprises one of the charges modified by a single currency exchange rate, the currency exchange rate being a factor of each value; converting by the verification agent computer system each of said received plurality of values to a respective value ratio by dividing by the verification agent computer system each of said plurality of values by the sum of said plurality of values; comparing by the verification agent computer system each of said value ratios to said stored charge ratios; and verifying by the verification agent computer system authorisation of said transaction only if each of said value ratios matches a respective stored charge ratio within a predefined margin of error.