A change that, when made in a legal document, may affect its validity. An alteration in a will is presumed to have been made after execution and will therefore be invalid. However, it will be valid if it is proved to have been made before execution or if it was executed in the same way as the will itself. If the alteration is duly attested by the testator and the witnesses placing their initials or signatures by it, it is presumed to be valid. If an invalid alteration completely obliterates the original words, it is treated as a blank space. If the original words can still be read, they remain effective. Alterations in deeds are presumed to have been made before execution. Alterations made after execution do not affect the validity of the deed if their purpose is to correct an obvious error. If, however, a material alteration is made to a deed after execution without the consent of the parties, the deed may become void in part. See also amendment.