How do you form the passive with ser in Spanish?

Take ser in the tense you want, then add the past participle of the main verb, and make the participle agree with the subject in gender and number. El libro fue escrito (the book was written), la casa fue construida (the house was built), los libros fueron escritos (the books were written). The tense and person sit on ser - es vendido, fue vendido, será vendido, ha sido vendido - while the participle behaves like an adjective and matches the subject. If you name who did it, add por plus the agent: fue escrito por Cervantes.

What is the difference between ser and estar with a past participle?

Ser plus participle is the true passive and reports an action: la puerta fue cerrada means somebody closed the door, it was closed (the event). Estar plus participle describes the resultant state that the action left behind: la puerta está cerrada means the door is closed (how it is now), with no event in view. So la casa fue construida en 1900 reports the building of it, while la casa está bien construida describes its present condition. The same participle, a different auxiliary, a different meaning.

Why does Spanish avoid the passive with ser?

Because it has better-liked alternatives. Where English reaches for the passive, Spanish usually prefers the passive se (se venden casas, se habla español) or simply turns the sentence around into the active. The ser-passive survives mainly in formal and written registers - journalism, history, official prose - and especially when you want to name the agent with por: la novela fue escrita por una autora desconocida. In everyday speech it sounds heavy, and a native speaker would more often say se vendió la casa than la casa fue vendida.

The Passive with ser in Spanish

English builds passives constantly: the book was written, the house was built, the law was passed. Spanish has the very same construction - ser plus a past participle - but treats it as a marked, formal choice rather than the everyday default. Before you can use it well, you have to know two things it does that English does not, and one trap that looks identical but means something else.

This page assumes you can already build the past participle and that you have met ser vs estar, because the whole topic turns on which of the two you pick.

The one structure: ser + past participle (+ por + agent)

The true passive is ser in whatever tense you need, followed by the past participle of the main verb.

El libro fue escrito por Cervantes. (The book was written by Cervantes.)
La casa fue construida en 1900. (The house was built in 1900.)
El coche será vendido la próxima semana. (The car will be sold next week.)

The thing the passive is about - the book, the house, the car - becomes the grammatical subject. Whoever did the action, if you mention them at all, comes in with por: por Cervantes, por el viento, por una autora desconocida.

The participle agrees with the subject

This is the first thing English does not do. In Spanish the past participle in a ser-passive behaves like an adjective: it agrees with the subject in gender and number.

El libro fue escrito. (masculine singular)
La novela fue escrita. (feminine singular)
Los libros fueron escritos. (masculine plural)
Las cartas fueron escritas. (feminine plural)

So you cannot just memorise one form. Construido becomes construida, construidos, construidas; vendido becomes vendida, vendidos, vendidas. Match the ending to the subject every time, exactly as you would with any adjective.

The tense lives on ser

The second difference: all the grammatical work - tense, person, number - sits on ser, never on the participle. You change ser and leave the participle to agree.

El libro es publicado cada año. (present: is published)
El libro fue publicado en 1605. (preterite: was published)
El libro será publicado en otoño. (future: will be published)
El libro ha sido publicado en muchos países. (perfect: has been published)

Notice the perfect: ha sido publicado stacks the participle of ser (sido) and then the main participle. The pattern is regular - put ser into the tense you want and the passive follows.

ser versus estar: action versus state

Here is the trap. Estar plus a past participle also exists, but it does not report an action. It describes the resultant state the action left behind. Same participle, different auxiliary, different meaning.

La puerta fue cerrada. (ser) - The door was closed: somebody closed it, an event.
La puerta está cerrada. (estar) - The door is closed: that is how it is now, no event in view.

The ser version reports something that happened; the estar version describes how things are. Compare:

La casa fue construida en 1900. (It was built in 1900 - the building of it.)
La casa está bien construida. (It is well built - its present condition.)
El problema fue resuelto por el equipo. (It was solved by the team - the event.)
El problema ya está resuelto. (It is already solved - the state.)

A quick test: if you can add por plus an agent, you want the action, so ser. If you are describing how something looks or stands right now, you want the state, so estar.

Why Spanish reaches for it so rarely

Worth saying plainly, because it changes how you should write. Spanish uses the ser-passive far less than English does. Where English happily says "the house was sold", a Spanish speaker will usually prefer one of two things:

the passive se: se vendió la casa, se venden casas, se habla español;
or a plain active sentence: vendieron la casa (they sold the house).

The ser-passive survives mainly in formal and written register - journalism, history, official prose - and above all when you want to name the agent with por: la novela fue escrita por una autora desconocida, la ciudad fue fundada por los romanos. If there is no agent to name, the se-passive almost always sounds more natural. Reach for ser when the register is formal and the por is doing real work; otherwise let se or the active carry it.

Worked examples

El cuadro fue pintado por un artista famoso. (The picture was painted by a famous artist.) - agent named with por.
Las casas fueron construidas el año pasado. (The houses were built last year.) - feminine plural agreement.
El coche ha sido vendido. (The car has been sold.) - perfect, ha sido + participle.
La ley será aprobada en otoño. (The law will be passed in autumn.) - future on ser.
La puerta fue cerrada por el viento. (The door was closed by the wind.) - action, ser.
La puerta está cerrada. (The door is closed.) - state, estar, no event.

Common mistakes English speakers make

Not making the participle agree. Writing la casa fue construido or las puertas fueron cerrado copies the single English form. The participle is an adjective here: la casa fue construida, las puertas fueron cerradas. Match gender and number to the subject every time.

Putting the tense on the participle instead of ser. There is no "fued" or "será-do". The tense lives on ser alone: fue vendido, será vendido, ha sido vendido. Conjugate ser and leave the participle to agree.

Using ser where Spanish wants estar. Saying la puerta fue cerrada to mean "the door is shut (now)" reports an event you did not intend. For the present state, use estar: la puerta está cerrada. Ask whether you mean the happening or the condition.

Overusing the passive at all. Translating every English passive word-for-word gives heavy, foreign-sounding Spanish. Most of the time the passive se - se vende, se venden - or a plain active sentence reads far better. Save the ser-passive for formal prose and for when you are naming the agent with por.

Get the agreement, the tense-on-ser rule and the ser-versus-estar split straight, and the passive with ser is mechanical. The harder skill is knowing when not to use it - and that is what the next page is for.