A US Doctor working in Australia would like to establish a DB Plan. Doctor has his own US "S" corporation established that receives his Australian income and pays him as an employee. Question is, can he use his gross income as shown on his 1040 before the foreign tax credit? He pays Australian income tax on his earnings and then gets a foreign tax credit on his 1040. Couldn't the DB Plan be based on his 415 compensation?

The Doc need to consult with a tax advisor to determine his compensation. You can check IRS pub 560 available at irs.gov or instructons for IRS form 1120.