It is always allowed for a married couple to file jointly even if one spouse does not work or has very little income, or their income is only from Social Security. Married filing jointly almost always results in the lowest overall tax or largest overall refund. Your spouse’s Social Security may be partly taxable depending on your total combined income.
Furthermore, as mentioned, if you file separately, then your spouse must file separately and their Social Security becomes taxable; they may pay more tax on their Social Security income by filing separately than if you filed jointly.
