C Form

"C" Form is to be issued within 3 months of the end of the
month in which the transaction took place.
IS the C form to be issued for each and every purchase with
the same supplier ? For how long is the C form valid ?
And what happens in case of the supplier if after promising to submit C form,
the purchaser subsequently doesnt do so ?

Is the above mentioned info correct and pls ans my questions with examples if necessary..!!