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You need the address to charge them the _correct_ sales tax. In Washington State, the rate is based on the address where the product is delivered, so in the case of your example sandwich, that's the address of the deli.

Because you’re in the physical location, so you have to abide by that tax law. You’d need at least the zip code of someone to charge appropriate taxes for where that person physically is.

I would need your address to know whether and how much tax to charge you