Tag é uma pergunta curta e rápida no final de uma frase para se pedir uma confirmação do que se disse antes.

Examples:

He is a doctor, isn't he? (Ele é um médico, não é?)
Quando a 1 Parte da frase for afirmativa, a segunda parte será negativa.
He isn't a doctor, is he? (Ele não é um médico, é?)
Quando a 1 Parte da frase for negativa, a segunda parte será afirmativa.

- Com verbos auxiliares:

Examples:
It is hot today, isn't it?
Paul is a good boy, isn't he?
She was here, wasn't she?
They were friend, weren't they?
Mary has a car, hasn't she?
She can't run, can she?
They could work, couldn't they?
You should do this, shouldn't you?

- Com verbos não auxiliares:

Empregamos as formas verbais:
do, does, don't, doesn't para o presente
did, didn't para o passado

Examples:
You know England, don't you?
You don't live here, do you?
She doesn't speak English, does she?
You knew England, didn't you?
She didn't speak English, did she?

- Future and Conditional:

Examples:
You will go, won't you?
He won't come on time, will he?
She would come, wouldn't she?
He wouldn't go, would he?

Tip:

- Para a 1 pessoa do singular I, a tag question tem uma forma irregular.
Ex.: I am your friend, aren't I?

Por: English Plus English