All over this forum are requests for adding or changing customer registration fields. This could be achieved implementing a Customer Attributes (such as tax/VAT number, sizes for clothing stores, number or age of children for toys or babies stores; hobbies or interests,; etc.) feature, similar to product or checkout attributes. In this case there should be an option to set the customer attribute as optional or required
This feature has been highly demanded. For instance check: https://www.nopcommerce.com/boards/t/7140/how-to-add-social-security-number-to-customer.aspx https://www.nopcommerce.com/boards/t/5274/how-to-use-nop_customerattribute-table.aspx#32658 https://www.nopcommerce.com/boards/t/2931/custom-customer-address-fields.aspx https://www.nopcommerce.com/boards/t/4518/nopcommerce-v160-released.aspx?p=5 https://www.nopcommerce.com/boards/t/6529/custom-attribute.aspx ...