For a given tax year, how does one use the information provided in their P60 to calculate how income should be declare to the IRS?
As I understand in the U.K. a tax year is between 6 April to 5 April. While in the U.S. it is between January 1 to December 31. For example, pertaining to U.S. tax year 2016, is it reasonable for a U.S. expat (i.e. permanently residing in the U.K.) to use each payslip, for the year 2016, to calculate total (foreign) income? Furthermore, should foreign income be calculate from gross or net?