A guarantee given on a bill of exchange or promissory note by a party who signs the instrument itself, usually a bank, undertaking to answer for one of the parties liable on it. Because the undertaking is written on the instrument, the avalising party is liable on the instrument in the same way as the party for whom the aval was given, and a holder taking the paper takes the benefit of it — which is why avalised paper is bought and discounted in forfaiting. It is a civil-law concept; common-law systems reach broadly similar results through endorsement or a separate guarantee, with different consequences. Whether an aval is available at all depends on the law governing the instrument.
Why this entry carries no source list. This is a product category or an official document type rather than a defined term. What it covers or attests is set by the policy wording, the facility terms, or the requirements of the country demanding it — and those differ by insurer, by bank and by jurisdiction. Naming one provider’s brochure as the authority would dress a single firm’s practice as a general rule. Read the wording you are actually being offered.