When you use M1 Borrow, interest will accrue for each day that you utilize your portfolio line of credit and you are billed on a monthly cadence.
Your bill we be available at the end of each month, and you will only need to pay for the line of credit borrowed. You will be charged on the due date of your bill (before the daily trade window).
When charged, the amount due is automatically deducted from your M1 cash balance. If there is not enough cash to cover your bill, M1 will extend additional credit to cover the amount. Please note, if you have neither cash nor credit available, M1 will sell holdings from your portfolio to pay your interest due.