明白了。還有一個小小疑惑：

“Another tax benefit if you file 1040 is you can claim child tax credit (if you have at least one child and income under certain threshold).“

如果claim tax treaty, Federal tax 應該100%退，還有必要claim child tax credit 嗎？

另外關於州稅，是不是各個州規定不同，我搬來PA,這裏的朋友說PA的州稅不能 covered by tax treaty.

謝謝。