I started receiving my retirement benefits from SSA last October 2019 after 2 years of processing time. They paid me a large sum corresponding to all months (25) of back pay and I received also my payments from October to December. All these payments had federal income tax withheld to 25% which amounted to a large sum that I want to have refunded.
My question is that I do not see in what line of form 1040nr I should report the income. In the form shows where I should attach the form SSA-1042S but in that area only show lines for the form 1042S and not SSA-1042S.