Payments are calculated based on the outstanding line balance each month. You can always pay off your outstanding balance at any time.
Because HELOCs are lines of credit, monthly payment amounts are not usually fixed.
During the draw period, you will be required to make monthly payments of accrued interest, plus any principal balance in excess of your credit limit. Please note that if you only pay accrued interest during the draw period, your monthly payment during the repayment period may increase substantially.2
During the repayment period, you will make monthly payments that are calculated based on your outstanding balance at the end of the draw period, plus accrued interest and other fees, charges, and costs.2 Refer to your credit agreement for details on how your lender calculates payments during the repayment period.