Should Buddhists avoid Amazon and Starbucks out of concerns about tax avoidance? Recently companies such as Starbucks and Amazon were accused of avoiding paying UK tax. Many people were quite upset about this and people began to boycott those companies involved. From a Buddhist perspective is there any problem with this? The companies are not stealing nor are they breaking any laws - tax avoidance is perfectly legal as opposed to evasion which is not.

I appreciate there are many arguments that could be made against this practice around fairness, justice, social responsibly etc... However I'm interested in the Buddhist angle - perhaps thinking about the precepts or maybe broader concepts such as karma and dependent origination or another aspect of Buddhist thought that I'm not aware of.
I think the answer is No. You can, but due to your personal views and believes, it has nothing to do with Buddhism, from a Buddhist's perspective you should take care of your actions, they will receive the results of their kamma (if any). Focus on what you do and left undone as the Buddha taught.

Another thing is that these days almost 99% of the companies do some kind of tax planning that involves similar practices, you just don't know it.

In an extreme example imagine if someone says: I will not pay taxes because the government is corrupt, that is wrong, as a citizen you should pay taxes and the politicians will face, sooner or later, the consequences of their actions.