Internal Revenue Service (IRS) responsible for collecting taxes and assisting taxpayers can choose to audit anyone's taxes from the last 3 years. They use services from the likes of a New York based startup, an expert in blockchain analysis, Chainalysis, started in 2014, to track bitcoin users who evade taxes. So, any evasive activity which might not come under scrutiny now can retrospectively cause you fines and penalties.
We have no choice but to pay the tax required for many transactions especially in USA where the IRS is really serious in doing its job of running after tax evaders. I have no problem with tax but sometimes the government has an annoying habit of overtaxing people...this is not good for the economy and for individuals. So what are the things that the government is offering in return for stricter cryptocurrency transaction tax? The best thing to do is to come up with a package which can make everybody happy while the government is also smiling collecting their revenues. Anyway, it is still good that the government of US has not followed the myopic approach made by China last September.