I am a US citizen living in Canada. I have no income from any source in the USA. My only income in canada is Old Age Security benefits and Canada Pension Plan income as well as a small amount ($3400) from mutual funds. What forms do I submit to the IRS and how do I claim the foreign tax already paid.

Then you must have dual citizenship if you collect CDN OAS and CPP?

You will submit Form 1040 with Form 1116 to claim the Foreign Tax Credit as it applies to the mutual fund. The pensions, if taxed by Canada, are exempt by treaty from U.S. taxation.

FYI, Atlanta, old age security and canada pension are taxable for Canadians.

Yes, that is what I thought to be the case.

Thank you. So if I understand correctly, I do not enter my OSS and CPP benefits anywhere.

That is correct.