Your contribution basis in the Roth IRA is the basis transferred from the TSP Roth plus the $6,500 regular contribution basis. If the distribution from the TSP Roth that was rolled over to the Roth IRA would have been a qualified distribution from the TSP Roth (at the time of the distribution from the TSP Roth, age 59½ or over and more than 5 years from the beginning of the year in which you first made a TSP Roth contribution) had it been paid to you, the entire amount rolled over is now considered contribution basis in your Roth IRA. If it would not have been a qualified distribution from the TSP Roth, only your original TSP Roth contribution basis (shown in box 5 of the Form 1099-R reporting the distribution from the TSP Roth) became contribution basis in your Roth IRA.
