10% annual interest on up to $10,000 (principal plus interest); money above $10,000 earns nothing.
Eligible after 30 consecutive days (or 1 day in each of 3 consecutive months) in a combat zone, or in a hazardous duty / direct-support area while getting hostile fire or imminent danger pay.
Deposits of $5 or more from unallotted pay and allowances, by allotment, cash or check.
SDP interest is taxable (per CFPB).
How to apply
How to get it: Ask your finance office to start SDP deposits by allotment, cash or check.
Uses the TSP formula: 1% automatic + 100% match on your first 3% + 50% on the next 2%. Matching starts after 2 years and 1 day of service for new members.
Enter your basic pay to see your match.
Basic pay only. Special pay and bonuses aren't matched. Estimate, not a guarantee. Formula from TSP.gov, checked Oct 20, 2026.