Home TSP TSP Rates of Return September 2019 TSP TSP Rates of Return September 2019 October 3, 2019 2608 0 Share on Facebook Tweet on Twitter tweet Most Thrift Savings Plan funds showed modest gains for the month of September 2019. Only the F Fund had a negative return for the month. YTD, the C, S and I Funds are showing strong gains for the year.