How do I claim a full time dependent, but decline to collect the Child Tax Benefit payment every month?

The CRA only uses the tax returns of the parents to determine income levels for the Child Tax Benefit. To apply for the CCB you have to fill out a form that’s not part of a personal tax return, so if you want to stop those payments you would need to contact the CRA: https://turbotax.community.intuit.ca/replies/2647704