One. The TSP is an individual account and you can only roll money into it from a qualified individual account that is yours. You cannot roll your spouse’s 401(k) from a prior employer into your TSP. If your spouse has qualified money that they wish to roll over, they can set up an IRA in their name with another custodian.
Two. The TSP can only be funded by payroll deduction or by a rollover from a qualified plan. If you have money in a non-qualified account, it cannot be deposited in the TSP. So, Aunt Kate’s bequest, lotto winnings, etc. cannot go into the TSP.
Three. When you are old enough (i.e., when you reach the year in which you turn 50) to make catch-up contributions ($6,000 in 2017), you need to make a separate allocation for the catch-up contributions. If you simply increase your regular TSP contributions, they will stop when you reach the elective deferral amount ($18,000 in 2017) and you will lose matching contributions for the remainder of the year.
Four. Contribution allocations and interfund transfers are two separate actions and affect your TSP account differently. A contribution allocation change only affects the money you are putting into the TSP, it does not re-allocate money already there. An interfund transfer only affects money that is already in your TSP, it does not change future contributions.