TP spouse with Japenese social security

[Tracy Lee]

TP's wife who has lived in the US for 30 years (green card) starting receiving her Japanese social security this year.  She says she doesn't have to pay taxes because it's taxable in Japan even thought she paid no taxes on it because it's below her filing threshold.   I have other clients in similar situation from UK and one from Norway and they always report their small incomes and pay taxes on it.  From my research the Japanese social security is taxable here in the US.  She does not go to Japan, has no home there or job either.  Is there any other reason it wouldn't be taxable?  Otherwise it is right?

[Pacun]

I guess you have to start with the US-Japan tax treaty.