Do I need a tax ID in order to sell things at an art market or craft show?

Answer 1

Most likely, laws vary by state. All you need to do is contact your state comptroller office.
(In my state, you are allowed to sell your own personal property at a garage sale without collecting sales tax, but you are limited to two garage sales per year.)
In order to re-sell merchandise at a market or craft show, you will probably need to collect local sales tax. (Check the amount, it can vary from city to city within a state.) Then depending on your volume of sales, you may be required to fill out a form and pay the tax back to the state government annually, quarterly, monthly, or weekly. It's just a matter of good record keeping, and holding onto copies of your purchases and sales for several years in the event you are audited.

Answer 2

It depends on where you live, but as a general rule of thumb: Yes. If there are tax people at the craft show and you don't have one they will shut you down unless you can prove that you make less than a threshold amount of money. It varies from place to place and it can be as little as 500$ a year to as much as 5000$ a year. And sometimes different cities and municipalities have different rules. It's always a wise investment to find out what licenses you need a get them rather than risk being shut down and losing any money you have made. There's another reason to get proper tax papers: a big benefit of a tax number is that you can save boatloads of money by buying craft supplies in bulk wholesale. That alone makes the license a wise investment.