To make the election or enter the details of a previous election to stop paying CPP on your Self-Employed earnings using TurboTax Online or in the EasyStep view, go to Income > T-Slips > T4A(P) Canada Pension Plan Benefits.

On the T4A(P) - Summary screen, you can enter your information about previous elections or choose to stop contributing to CPP on your self-employment earnings. You must say "Yes" to the question - "Did you elect to stop contributing to CPP on your self-employment earnings in a year prior to 2017?"

This screen will only appear if you were 65 to 70 years of age. 

How about if I am under 65 and would like to stop contributing to CPP on my self-employment earnings?

You cannot choose to stop contributing to CPP (Self-Employed or Employee) until you turn 65. This link provides all the CRA rules on stopping your CPP contributions: https://bit.ly/2SYltJc

Thanks for that tip. This was for the 2021 year, but I followed what you said and was able to get to the question to stop CPP on my self-employed income for 2021. Before this I could not find that question and I couldn't get schedule 8 to let me change it. I was going bonkers. Thanks so much!!!