Kamran has paid the bill.

1. The bill had been paid by Kamran.
2. The bill has been paid by Kamran.
3. The bill was being paid by Kamran.
4. The bill is being paid by Kamran.

The original sentence is in present perfect active voice: “Kamran has paid the bill.” To convert to passive voice, the object becomes subject, auxiliary “has been” is used, and past participle “paid” follows, with optional “by Kamran.” Present perfect passive structure: has/have + been + past participle. This transformation maintains the original tense while shifting focus from subject to object.