What was the tea act and why was it established ?

In 1773 it was establised by the British Parliament to essentially save the East India Company from bankruptcy. It greatly lowered the Tea Tax it paid to the government. It was a tea tax on any imported tea from Britain. The effect of this? The Sons of Liberty organized a protest against the Tea Act known as the Boston Tea Party. They dumped 342 chests of tea, imported by the British East India Company into the harbor. They declared the famous "taxation without representation" slogan while doing so.

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mostly drug tunnels for drug deals etc.

the answer is: must pay taxes on profits

since it is considered as a part of your income, profits from investments is eligible for tax payment.

the tax from your investment could be influenced by how long you decided to sell it. united states promotes keeping your investment for long term period. so, the tax rate for investments that you sell in less than one year is typically higher compared to investments that you sell in more than one year period.