Should I provide my transcripts for all years or only the last year? I am applying for a a PhD in the UK, and they ask for my bachelor transcript. Should I only include the third year transcripts or full three years ? Since I am translating it from another language it is better for me to only include the last year
This may vary by university, but a transcript is a full academic record of your time at an institution. As such, they will expect information on every course that you took, all three years. A partial transcript is obviously acceptable for degrees which have not yet been completed, but omitting completed courses may look like you have something to hide.

There will likely be a firm requirement to provide a full original transcript, and if not in English, an authorised translation, before your place is confirmed, regardless of whether a partial transcript is acceptable for an offer to be given.