When you win auction items, the Tax ID (EIN) of the organization will be included on the receipt automatically sent to you after the auction. Here's an example:

Whether your contribution is tax-deductible depends on your personal situation, so it's always a good idea to consult a tax professional.

In general, the tax-deductible amount is the difference between the amount you paid and the fair market value of the item. The receipt you receive will include the estimated fair market value of the item to help you determine your deduction.