grammatical problem

[azade]

Is this sentence true or I should use ''has been'' instead of ''was''?
The final version of the proposal, which was confirmed by the committee members, has been attached.

[emsr2d2]

Is this sentence true correct or should I should use ''has been'' instead of ''was''?
The final version of the proposal, which was confirmed by the committee members, has been attached.

Welcome to the forum.

Check the difference between "true" and "correct".

I would word your sentence this way:

A copy of the final version of the proposal, which has been confirmed/authorised by the committee members, is attached.

I am working on the assumption that you are attaching a copy of the proposal to the email/letter which contains this sentence.

[5jj]

Welcome to the forum, azade.

"Has been" or "was?" would have been a more relevant title for your thread. (See the second line of my signature.)