The single highest guaranteed return available to anyone on active duty is the Savings Deposit Program, and it only exists during a qualifying deployment. In the guides we publish here, we build every wealth-building sequence around what is available right now versus what runs every pay period.
The Savings Deposit Program Pays 10% Guaranteed, Only While Deployed
The Savings Deposit Program (SDP) pays 10% annual interest, compounded quarterly, on up to $10,000 you deposit while serving in a designated combat zone, hazardous duty area, or qualifying contingency operation. That rate is set directly by 10 U.S.C. Section 1035 and has not moved since 1966. Nothing else available to a service member matches a guaranteed 10% return with zero market risk.
Eligibility requires 30 consecutive days, or at least one day in each of three consecutive months, in a qualifying location. You can deposit unallotted pay, including bonuses, up until your last day in the combat zone, and the account keeps earning for up to 90 days after you return. Deposit early in a deployment rather than late. Every extra month your money sits in SDP is another quarter of compounding you cannot recover once the deployment ends.
Fund the TSP Match before SDP, Every Time
The Blended Retirement System (BRS) matches your Thrift Savings Plan (TSP) contributions up to a set percentage, and that match runs every single pay period, deployed or not. SDP's 10% only exists during a deployment window. Fund TSP enough to capture the full match first, then route any extra unallotted pay into SDP once you are actually deployed. Reversing that order means giving up free matching money in exchange for chasing a rate you would have captured anyway during the deployment.
Check your current contribution percentage against the BRS match schedule before your next deployment starts, not during it, so you are not scrambling to adjust an election from overseas.
The Combat Zone Tax Exclusion Changes What "Extra" Money Means
Deployed pay to a designated combat zone is excluded from federal income tax under the combat zone tax exclusion, which our full guide covers in detail. That exclusion means a dollar of deployed pay stretches further than the same dollar earned stateside, since none of it goes to federal tax first. Combine that with SDP's 10% and TSP's match, and a single deployment can fund all three levers with pay that would otherwise be taxed the moment it landed in your account stateside.
A Six-Month Deployment, Worked Out in Numbers
Say you deploy for six months with your TSP contribution already set to capture the full BRS match, and you direct $500 a month of unallotted pay into SDP starting on arrival. By month six, you have deposited $3,000 into SDP. At 10% annual interest compounded quarterly, that produces roughly $75 to $100 in interest by the time you factor in the 90-day post-deployment accrual window, on top of whatever your TSP balance grew from contributions and the match during the same six months. The SDP interest itself is a modest dollar figure on a short deployment. The 10% guaranteed rate is what matters, since no other account anywhere pays that on new deposits.
SDP Resets with Every Qualifying Deployment
The $10,000 SDP ceiling applies per deployment, not once across your entire career. Someone who deploys three separate times gets three separate chances to fund an account up to $10,000 at 10%, as long as each deployment independently meets the 30-day or three-consecutive-month test. A career with several deployments compounds this benefit in a way a single-deployment view misses entirely, since each qualifying tour reopens the full $10,000 ceiling from zero.
Withdraw and close out your SDP balance after the 90-day post-deployment window on one deployment before assuming the next deployment simply continues where the last one left off. Each account resets, and treating them as one continuous pot risks missing the withdrawal deadline on an earlier deployment's balance.
SDP Against the Alternatives, Side by Side
| Feature | SDP (during deployment) | TSP Match | Civilian High-Yield Savings |
|---|---|---|---|
| Guaranteed rate | 10% fixed by statute | Varies with BRS match formula, not a rate | Market rate, moves with the Fed |
| Available when | Only during a qualifying deployment | Every pay period | Anytime |
| Contribution cap | $10,000 per deployment | Set by BRS match percentage | None |
| Risk | None; government-guaranteed | None on the match; TSP funds carry market risk | None, FDIC-insured up to limits |
Reenlist-or-Separate Timing Interacts with All Three Levers
A decision to reenlist or separate changes how much runway you have to repeat this sequence on future deployments. Our reenlist or separate financial math guide covers the pension, TSP, and civilian-offer comparison in full. Someone weighing separation against a near-term deployment should factor in that SDP access ends the day you leave the combat zone for good, along with the match, while a civilian 401(k) offers neither a guaranteed 10% nor a combat zone tax exclusion.
Who This Is Not For
None of the SDP guidance here applies to a service member who has never deployed to a designated combat zone or qualifying contingency operation, since eligibility requires that specific deployment status. This sequencing also does not fit someone already carrying high-interest debt, a credit card balance well above SDP's 10% rate. Paying that debt down first beats depositing into SDP, since eliminating a higher interest rate is a better guaranteed return than capturing a lower one.
What Would Change This Answer
A deployment shorter than 30 days changes the picture entirely, since it falls under SDP's minimum eligibility window and none of the SDP guidance applies. An unusually short remaining service commitment also changes the math on the reenlist-or-separate comparison, since fewer future deployments mean fewer chances to use SDP again. A TSP contribution already below the full BRS match percentage should get fixed before any SDP planning starts, since that free match outweighs SDP's rate on every pay period it is missed.
Confirm your TSP contribution captures the full BRS match before your next deployment, then set up SDP deposits through your finance office once you arrive in a qualifying location. See the combat zone tax exclusion guide for the tax side of a deployment, or reenlist or separate financial math for how these pieces fit a longer-term career decision.
This page is general information, not legal or financial advice. Verify your specific eligibility and current SDP/TSP rules with your finance office before acting.