I am not aware of any specific percentage/portion of sales or proceeds that must be paid to a charity to consider it a “charitable event.”  The key issue usually is whether there are sales based on a “charitable appeal,” urging patrons to buy because a portion of the proceeds will be paid to a charity.  When you make this appeal you probably become a “commercial co-venturer.”

You ought to be sure that the charity is registered to solicit charitable funds (or have funds solicited on its behalf) if required in any state in which you will make the charitable appeal.  39 states plus the District of Columbia have such statutes. You should also check the law of those states to see whether you have to register as a charitable co-venturer.  A few states require it.  Several states require a written agreement with the charity and a few of them require it be filed for public view.  About 10 states require disclosure of the percentage of funds that will go to charity and the detail of how the charity will receive the money. (See Ready Reference Page: "Co-Venturing Can Benefit Both Business and Charity, But May Be Terminated by Disclosure Laws")