Policies vary, but most of the larger establishments require you to give advance written notice that you want to end your membership. Read the fine print of any document you sign, even if it's not a formal contract. Check gym websites to see if they have a posted cancellation policy. Never rely on a staff member's verbal explanation of how to cancel. Get the policy in writing before you join the gym. If you have a problem with a gym that continues to charge your credit card or bank account, contact the financial institution to stop payment.