The law in texas is that foreign entities transacting business in texas must register in state. However, what constitues transacting is not technically defined, the state instead chose to define some of what is not considered transacting business. However, the criteria for triggering the franchise tax is lower so that more businesses are subject to it. (Texas wants it's share of your pie!)
Here is the exact wording from our SOS page:
Transacting Business in Texas: A foreign entity that is transacting business in Texas must file an application for registration with the Texas Secretary of State. Whether an activity constitutes "transacting business" in Texas is often difficult to answer. Texas statutes do not define “transacting business;†however, Texas Business Organizations Code (BOC) § 9.251 lists activities that are not considered transacting business. Case law and Attorney General Opinions are useful in determining whether or not an entity is “transacting business†in Texas. The secretary of state cannot issue opinions on whether an entity is transacting business in Texas or needs to file an application for registration.
The level of a foreign entity’s activity in Texas that subjects it to franchise taxes is lower than the level of activity that subjects it to registration requirements. An entity that is doing business in Texas for purposes of franchise taxes may not necessarily be “transacting business†in Texas for purposes of registration with the secretary of state. If you need assistance in determining whether a foreign entity is subject to franchise taxes, you can submit a “Texas nexus questionnaire†(Form AP-114) to the comptroller of public accounts. Based on the answers to the questionnaire, the comptroller will issue an opinion about whether the entity is doing business in Texas for franchise tax purposes. For more information, visit the comptroller's website or contact
Link to our Secretary of state section that talks about this: http://www.sos.state.tx.us/corp/foreign_outofstate.shtml