Billing Process - Data Transformation Corporation bills quarterly, semi-annually, or annually for services 30 days prior your service period. Your initial payment is due on or before the first day of the service period. Invoices are sent to the email address listed on the service level agreement. Standard payment terms on all invoices are "net 30". ACH checking or VISA/Mastercard payments are processed through PaySimple. If you have any additional questions, please feel free to call DTC's Billing Department at 301.587.4580.