Looking for anyone who as found specific (official) comments about where the tax ends, relative to in-state or out of state. I don't see any question about the boundry however I have heard of some local discussions that differ. I will add a fairly educated (but not official) comment about taxability of out of state sales to Mass DOR - I am not aware of a case where selling to an out of state client is taxable, where they are physically out of state of Mass. If you have a legal presence in some other state (for their sales tax purposes) then local rules in that area might apply, but not for Mass Tax purposes. There is a whole discussion of a MPU (Multiple Points of Use) certificate relating to web sites and cases with both in-state and out-of-state clients - this is different and requires a customer in Mass. References: http://www.mass.gov/dor/utility/recent-tax-changes.html and specifically http://www.mass.gov/dor/docs/dor/law-changes/faqss-computer-software-2013.pdf Item 17 http://www.mass.gov/dor/businesses/help-and-resources/legal-library/tirs/tirs-by-years/2013-releases/tir-13-10.html III.C