This is an irregular verb with a spelling change. It follows the conjugation pattern of the verbs cerrar and llegar.
PresentPresente
El banco deniega muchas solicitudes de crédito.
The bank denies many credit applications.
PreteritePretérito indefinido
Le denegaron la visa el mes pasado.
They denied him the visa last month.
FutureFuturo
La oficina denegará las solicitudes incompletas.
The office will reject incomplete applications.