[jjeaff]

First thing to note here is that the IRS does not care about what states your offices are in or whether you have a physical presence or not in those states. If the accounting firm told you this, I would seek a second opinion from an individual, but skilled and experienced CPA. The IRS is only concerned with federal taxes. They do not deal with any individual state laws.

Second, if it is a pure SaaS product, I am yet to see anyone anywhere in the US charging sales tax. Most states specifically do not tax services which includes SaaS. This article breaks down a few... http://blog.taxjar.com/saas-sales-tax/ You will note that there are some that require taxes and if you have employees in some of those states, you might take a look.

Thirdly, as an example, the laws in the state of California state that if a certain percentage of your work force are in the state, then you would need to register and file income taxes in that state. I had a US based SaaS startup with remote employees in multiple and firms were always trying to raise concerns about how we needed to file income tax in every state we did business. It would have been an enormous undertaking and is just not necessary.

Lastly, you probably do not have enough presence in the US to be considered having a tax nexus. My unofficial advice is don't worry about it. Accountants are like attorneys in that they are very conservative in the advice they give. No one is going to come after a small company like yours for not paying a portion of your income to their state because you have 2 or 3 remote employees there. The IRS is not going to try to get you to pay income tax if you don't have a big presence in the US. There is a 99.9% chance you will never be contacted by any of these agencies. And if you are, the worst that will happen is they will review your situation and try to get you to pay back taxes. After which you can hire a good firm to negotiate that away or down considerably. The IRS and especially state governments have very little jurisdiction on entities based outside the US. Things may change in the future, but for now, there is very little specific law on the books that would obviously require that you start filing and paying taxes all over the US.