Service agents must confirm customer contact information in the first step of a payment OmniScript. Contact information includes name, telephone number, mobile number, and email. None of the contact information on first step is required.

On the last step, after taking payment, the agent can optionally email the receipt to the customer. If the customer says yes, the agent selects a checkbox. If the agent selects the box but the email address field is empty, the process must require the user to return to the first step and enter the customer's email address.

What should the consultant recommend to meet this requirement?