It’s a very easy . If there is no bilateral treaty regarding Previsional matters to avoid double taxation , the foreign social security pensions are taxable. Do you want to know why? Because IRS take into consideration de “ saving clause”. See IRS webpage .
No need to substitute Form 1099 at all if it’s reported in Form 1040 line 8 Other income from Schedule 1 line 10 and obviously in such Schedule line 8z.
