Although you can purchase cryptocurrency while trading on margin with SoFi, it is not a marginable security. This means your crypto position must be fully paid, and it carries a 100% margin maintenance requirement.
As a reminder, when you purchase crypto, the funds are withdrawn from your Individual Active Invest account and moved to your Crypto account. If you made a withdrawal from your Individual Active Invest account to purchase crypto and withdrew more than your available Individual Active Invest account cash balance amount, you would have withdrawn some of your available margin balance.
This is considered a margin loan. When you withdraw any amount from your available margin balance, you will be charged interest the same as if you had used the available margin balance to purchase a stock or ETF.
How does margin work?