Yes, you do, unless you can provide a filled-out exemption form from the state. You can find the form here. If you are a qualified farm, simply print out the form, fill it out, and give us a signed copy for our records; then we can remove WA state sales tax from your invoice. The state is very strict in enforcement of this policy, and sellers can incur large fines if the do not have the exemption paperwork on file. So regrettably, we must charge you tax unless you can provide the form before or at the time of purchase.
If you are an out-of-state buyer and can prove residency outside of WA (e.g. with a driver’s license), you also do not need to pay sales tax.