The technical explanation to the US/Italy double tax treaty (at p.58) states that that distributions from  qualified plans under section 401(a), individual retirement plans (including individual retirement plans that are part of a simplified employee pension plan that satisfies section 408(k), individual retirement accounts, individual retirement annuities, section 408(p) accounts, and Roth IRAs under section 408A), constitute “pension” income provided they are made “consideration of past employment.  There is no specific mention of  401k schemes, and since only certain kinds of distributions are covered, specific advice needs to be sought. The main point to note is that access to the 7% regime depends on the taxpayer being in receipt of “a pension”. There is no doubt that SS benefits constitute  “pension” for these purposes (unless that are pensions relating to government service to which special rules apply. The SSA benefits will permit the taxpayer to access the 7% regime at which point, all other income and gains will fall to be taxed at the special regime for the period the relief applies.  A problem only arises where the taxpayer has no SS pension (or who has such a pension in relation to services provided to goverment.