Sales tax statement in online auctions

Yes, you should include a sales tax statement. Here's an example to consider: "Note to Residents of [insert state]: Sales tax will be added to your winning bid."

In most states, you're not allowed to add sales tax to a buyer's winning bid unless you tell them in advance that you will do so. Failing to include an advance warning in your Terms and Conditions policy will force you to "eat" the sales tax if a smart buyer complains.