No, because TSP are already deferred, you cannot use them as an additional deduction.
Right, maybe I should reword....can I setup a Traditional IRA and deduct contributions (up to $5500 limit) in addition to taking advantage of TSP contributions being tax deferred (up to $18000 limit)?
Yes ... you can have both a TSP & an IRA and contribute to both BUT the IRA contribution may not be deductible based on your total income.
Thank you for the clarification. Yes, the TSP may affect the amount you can deduct. See the chart at <a rel="nofollow" target="_blank" href="https://www.irs.gov/retirement-plans/2017-ira-deduction-limits-effect-of-modified-agi-on-deduction-if-you-are-covered-by-a-retirement-plan-at-work">https://www.irs.gov/retirement-plans/2017-ira-deduction-limits-effect-of-modified-agi-on-deduction-if-you-are-covered-by-a-retirement-plan-at-work</a> (based on income not necessarily contribution)
Perfect! That's what I was trying to confirm. Thank you very much both of you for your help!
Also, just checked the link to the chart and it had an extra character at the end....here's the hot link:
<a rel="nofollow" target="_blank" href="https://www.irs.gov/retirement-plans/2017-ira-deduction-limits-effect-of-modified-agi-on-deduction-if-you-are-covered-by-a-retirement-plan-at-work">https://www.irs.gov/retirement-plans/2017-ira-deduction-limits-effect-of-modified-agi-on-deduction-if-you-are-covered-by-a-retirement-plan-at-work</a>