All 401(a) plans (including 401(k) plans) provide extension of the rollover period for offset distributions, indicated by code M in box 7 of the Form 1099-R. The federal TSP is also treated as a plan to which section 401(a) applies, so it too should provide this extension. In either case, check with the plan to see that the Form 1099-R will include code M to indicate an offset distribution.
