Canadian income subject to SE tax?

Client worked in Canada for the Ringling Brothers circus and received a Canadian Form T4A-NR issued by Ringling Brothers for services rendered.
Would this be subject to SE tax on his U.S. return?

It depends.

1401(c) says that if a taxpayers’ SE income is subject exclusively to a totalization agreement between the United States and the foreign country, then the SE income isn’t subject to U.S. SE tax.

So, is the client’s SE income subject to the U.S.-Canada totalization agreement? You will find it here:

https://www.ssa.gov/international/Agree ... anada.html

See also RR 92-9.