By law, a Death Certificate must be completed “immediately" after a doctor or nurse practitioner learns of the death.

Burial & Cremation Act: S. 46B: Certificate of cause of death in relation to illness.
(2) A medical practitioner or nurse practitioner who attended the person during the illness must, immediately after learning of the person's death, give a certificate of cause of death for the person's death if the practitioner -
  1. is satisfied that the person's death was a natural consequence of the illness; and
  2. has taken reasonable steps to consult with any health practitioner known to have attended the person during the person's illness.