doxo is a secure all-in-one service to organize all your provider accounts in a single app, enabling reliable payment delivery to thousands of billers. doxo is not an affiliate of Merrimack Valley Cardiology Associates. Logos and other trademarks within this site are the property of their respective owners. No endorsement has been given nor is implied. Payments are free with a Linked Bank Account. Other payments may have a fee, which will be clearly displayed before checkout. Learn about doxo and how we protect users' payments.