Opt out of health and dental insurance plan before paying the tuition. When does it reflect on account summary?

The opt out will not reflect on your student account. You still need to pay the charge to student account and then if approved, the opt-out are reimbursed by the student union via e-transfer - (usually around November).

The opt out is administered entirely by the student union.
 

Here are some links you might find useful: 

• Third-Party Sponsorships | Office of the Registrar | McMaster University

• GSA Health & Dental​ Insurance Plan: Health and Dental – Graduate Students Association of McMaster University

• McMaster Student Union Opt-Out: Opt-Out - MSU (msumcmaster.ca)
  "