An abatement (or rebatement) is a modification of a coat of arms, representing a less-than honorable augmentation, imposed by an heraldic authority (such as the Court of Chivalry in England) or by royal decree for misconduct. The practice of inverting the entire escutcheon of an armiger found guilty of high treason has been attested since the Middle Ages and is generally accepted as reliable, and medieval heraldic sources cite at least one instance of removing an honourable charge from a coat of arms by royal decree as an abatement of honour. Other abatements of honour implied by the addition of dishonourable stains and charges, appearing in late 16th-century texts, have never been reliably attested in actual practice. Additionally, as many heraldic writers note, the use of arms is not compulsory, so armigers are more likely to relinquish a dishonored coat of arms than to advertise their dishonor.