My friend is a US resident who lived abroad for the past several years. He had his company there and that was his source of income. Now he decided to move to US permanently. He wants to do a wire transfer around $150 thousand from his personal abroad account to his personal US bank account. Is there any tax that need to be paid or any forms to be filed?

There is no tax on the money transfer itself.

However, he will have to file paperwork attesting to the source of the funds. That could lead to questions about how the money was earned, which could be a problem if he failed to file as a U.S. tax return during the period when the income was generated.