Some verbs have no passive form, but the functions of the passive can be achieved by using a different verb

VARIATION IN THE PROPERTIES OF ENGLISH VERBS

English passive verbs typically comprise some form of BE and a “past” participle. Examples (with the BE part underlined) are is understood, was helped, were being copied, can be taken and should have been known. Sometimes BE is replaced by BECOME or informal GET, e.g. got hit, or even dropped altogether (see 192. When BE can be Omitted). Verbs that are not passive are usually called “active”.

Verbs vary in the choices they offer concerning the passive form. One type (e.g. SAY) is compulsorily passive with a particular type of subject noun (messages instead of speakers). Another type (e.g. INCREASE) can be active with any type of subject, but can also sometimes be passive (see 4. Verbs that…