You can input a foreign pension or non-US Social Security payments into TurboTax (and thus report them on a US tax return), by creating a "substitute" Form 1099-R (see attached sample screenshot) It does not matter whether the income was a one-time lump sum payment, or an annual (ongoing) pension stream of monthly payments. It still gets reported, and taxed, the same.
Alternatively (and also preferably as well, because it is easier to do), you can enter the foreign pension income on Form 1040, Line 21 as "other income" or "foreign pension." If you choose this way, then you won't have to create a substitute Form1099-R, by filing Form 4852. However, the end tax result (in terms of United States tax rate and amount assessed) will be identical under both methods.
