NOT A TEACHER
Hello, Nisha Shafi:
ACTIVE: Someone sent (past tense of "send") the invoice to your head office on April 17, 2017.
PASSIVE: The invoice was sent (past participle of "send") to your head office on April 17, 2017. send/sent/sent
Some more examples:
This letter was written yesterday (NOT "write"). write/wrote/written
This cake was bought yesterday (NOT "buy"). buy/bought/bought
This umbrella was left here yesterday (NOT "leave"). leave/left/left