Igual que do / does en presente, el pasado tiene su auxiliar: did — uno solo, para todas las personas.

	Presente	Pasado
pregunta	Do you like it?	Did you like it?
negativa	She doesn't eat meat.	She didn't eat meat.
respuesta corta	Yes, I do.	Yes, I did. / No, I didn't.

La regla de oro: el pasado ya está en did, así que el verbo vuelve a su forma base:

• Did you go? — nunca Did you went?
• I didn't buy it. — nunca I didn't bought it.

Didn't es la contracción de did not.