How old do I have to be to open a OneVest account? August 17, 2021 17:00 You need to be 18 years of age to open a OneVest account. Related articles What is a Tax-Free Savings Account (TFSA)? What types of accounts can I open with OneVest? Security Practices at OneVest Why does OneVest need my tax information? Can I open a joint TFSA?