Nevil - I'm sorry that I didn't check back here and see your question earlier.
We could not even find my husband's Gold Points card so I just printed the page from his account summary statement at
www.goldpoints.com and took that into TGI Friday's. The hostess did not know what to do but she found the people there who did know how to handle them.
The certificates you can purchase with your Goldpoints can only be used towards food and not towards tax or tip. They do not give change or leave unused money on the certificate like a gift card would do. So, if you spend $21.98 on food for two on a visit, your best bet would be to turn in one $15 certificate and pay the remaining part of your bill and tip in cash.