This is an irregular verb. It follows the conjugation pattern of the verb volver.
PresentPresente
Siempre devuelvo los libros a la biblioteca.
I always return the books to the library.
PreteritePretérito indefinido
Carlos devolvió la camisa porque era pequeña.
Carlos returned the shirt because it was small.
ConditionalCondicional
Yo devolvería el dinero inmediatamente.
I would return the money immediately.