Open your TSP account and you will find a short menu of funds with single-letter names. G, F, C, S, I, and then a column of L funds with years attached. Most federal employees pick something during their first week on the job, often a default, and then rarely look at it again. Years later, that quiet choice may be driving a large share of their retirement income.
The letters are not hard to learn. Each fund has a clear job, a clear index or structure behind it and a clear kind of risk. Once you can say in one sentence what each fund does, the menu stops feeling like a puzzle and starts feeling like a set of tools.
This guide compares all six groups in plain language: the five core funds and the L target-date funds. It shows what each holds, what can go wrong, how they have behaved in recent years and how to think about combining them. It is educational, not a recommendation for any particular allocation, and it is written with federal employees and retirees in Puerto Rico in mind.
The Big Picture: Six Fund Types, Three Jobs
Before looking at each fund, it helps to see how they fit together. The TSP menu is built around three simple jobs: protecting what you have, earning income from lending money and growing through ownership of companies.
Stability, Income and Growth
The G fund is the stability tool. The F fund is the income tool, since it holds bonds. The C, S and I funds are the growth tools, since they hold stocks. The L funds are not a new job at all; they are ready-made mixes of the other five, adjusted automatically as you approach retirement.
Understanding these three jobs helps you see why no single fund is “best.” A fund that excels at growth will move up and down more. A fund that protects your balance will usually grow more slowly. The right mix depends on when you need the money.
Why Most TSP Funds Are Index Funds
Four of the five core funds, F, C, S and I, are passively managed index funds. According to the TSP fact sheet published in the USPS Postal Bulletin and dated January 2026, they invest through commingled trust funds managed by BlackRock, and their returns are shown net of expenses and trading costs. An index fund aims to match a market benchmark rather than beat it.
That structure keeps decisions simple. Instead of betting on one manager, you own a broad slice of a market and accept the market’s results, good or bad.
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Meet the Five Core Funds
Each core fund covers a different corner of the market. The following profiles describe what each one holds and the main risk to understand. They are not rankings.
The G Fund: Government Securities Fund
The G fund invests in special Treasury securities issued for the TSP. Its defining feature is that the value of your balance does not drop with the stock or bond markets, which is why it is often described as the stability fund. According to the January 2026 fact sheet, it returned 4.40% in 2024.
The tradeoff is growth. Over long periods, the G fund can fall behind inflation, which erodes what your savings can buy. Heavy reliance on the G fund can feel safe while quietly limiting how far your balance can grow.
The F Fund: Fixed Income Index Investment Fund
The F fund tracks the U.S. Aggregate bond index, a broad measure of investment-grade U.S. bonds. Bond prices move when interest rates change, so the F fund can rise or fall. It returned 1.33% in 2024, and it was the only core fund with a negative return in 2026 through August, at about negative 0.16%, according to FedTools’ September 2026 report.
That performance illustrates the F fund’s role. It is not a “safe” fund like the G fund. It adds diversification and income, but it carries interest-rate risk, and some years it trails the G fund.
The C Fund: Common Stock Index Investment Fund
The C fund tracks the S&P 500, an index of large U.S. companies. It is the most widely used growth fund in the TSP. It returned 24.96% in 2024 according to the fact sheet, and it was up about 13.12% through August 2026 according to FedTools.
Large gains come with large swings. Stock funds can lose value quickly in a downturn, and a long timeline is what allows many investors to ride out those periods. The C fund is a core of many portfolios, but it is also concentrated in large U.S. companies.
The S Fund: Small Cap Stock Index Investment Fund
The S fund tracks the Dow Jones U.S. Completion Total Stock Market Index. In plain terms, it holds the U.S. companies that the S&P 500 does not, mostly small and mid-sized businesses. It returned 16.93% in 2024 and about 16.10% through August 2026.
Smaller companies tend to be more volatile than large ones, but they offer exposure to a different part of the economy. Many investors pair the S fund with the C fund to cover the whole U.S. market.
The I Fund: International Stock Index Investment Fund
The I fund invests in companies outside the United States. It originally tracked the MSCI EAFE index, but the board changed its benchmark to the MSCI ACWI IMI ex USA ex China ex Hong Kong index, a vote announced in November 2023. According to a report on the change, the new index covers about 5,600 companies across 44 markets, including emerging markets, and roughly 90% of non-U.S. market value.
The I fund returned 4.27% in 2024, and FedTools reports about 19.18% for 2026 through August. It also notes a 2025 return of roughly 32.45%. Those swings show why the I fund adds diversification but also volatility, along with currency risk when the dollar moves.
The L Funds: A Ready-Made Mix
Many federal employees never choose individual funds at all. They choose an L fund, and the TSP does the allocating for them. Understanding how these funds work helps you decide whether to use one.
How an L Fund Is Built
Each L fund is a diversified mix of the five core funds. It adjusts automatically as its target date approaches, shifting from more aggressive to more conservative. According to FedSmith’s coverage of the L 2075 launch, the allocation is adjusted quarterly.
You pick the fund with the year closest to when you expect to start withdrawing money, not the year you plan to retire from your job. That distinction matters for people who plan to keep working or delay withdrawals.
Newer Funds and the L Income Fund
The TSP recently shifted L funds to five-year increments instead of ten. The L 2075 fund launched on June 30, 2025, for participants planning to begin withdrawals in 2073 or later, and the L 2025 fund merged into the L Income fund that same year. L Income is designed for people already taking withdrawals.
Because L funds are built from the same five core funds, they do not add new holdings. They add a decision-making shortcut. Their returns differ by date: the January 2026 fact sheet shows 2025 annual returns of 9.36% for L Income and between about 15% and 22% for the longer-dated funds, reflecting different stock exposure.
Who L Funds Suit
L funds suit people who want a single, automatic choice and do not want to rebalance. They suit less well anyone with other substantial assets, a large pension or a specific plan that conflicts with the fund’s glide path. Because an L fund is designed around an average investor, it may be more or less aggressive than you need.
Comparing the Funds Side by Side
Numbers help, as long as you read them with care. Past returns describe what happened, not what will happen, and a single year can be misleading.
Recent Performance in Context
The following figures come from the January 2026 fact sheet and FedTools’ September 2026 report. They are shown for context only.
- G fund: 4.40% in 2024, about 3.00% through August 2026.
- F fund: 1.33% in 2024, about negative 0.16% through August 2026.
- C fund: 24.96% in 2024, about 13.12% through August 2026.
- S fund: 16.93% in 2024, about 16.10% through August 2026.
- I fund: 4.27% in 2024, about 19.18% through August 2026.
What the Pattern Shows
Notice how the order changes. The I fund was among the weakest in 2024 and among the strongest in 2026. FedTools notes that the leading fund by month changed seven times in the first eight months of 2026, and it cautions against chasing last month’s winner.
That is the main lesson of the comparison. Leadership rotates, so a strategy that depends on picking the next winner is fragile. A strategy built on your timeline and your tolerance for risk tends to hold up better.
Risk, Not Only Return
Every fund trades something. The G fund trades growth for stability. The F fund trades some stability for diversification. The stock funds trade stability for long-term growth. When you compare funds, ask about the worst year as well as the best.
How to Think About Choosing
There is no formula that fits every person, but a few questions bring clarity. Work through them in order, and write down your answers.
Start With Your Timeline
When will you need this money? Money needed within a few years usually belongs in lower-risk funds. Money you will not touch for decades can usually tolerate more stock exposure. Your timeline is the single most important input.
Retirement can last thirty years or more, so even people close to retirement often hold some growth investments. The question is how much, and that depends on your income sources.
Consider Your Pension and Other Income
Federal employees have an advantage most private-sector workers lack: a pension. A guaranteed income stream can allow more growth exposure in the TSP, because the pension covers a portion of your expenses regardless of the market. Social Security can serve the same role.
If your pension and Social Security will cover most of your basic costs, your TSP may be better positioned for growth. If they will not, you may want a steadier balance. A retirement planning calculator can estimate how much of your spending is covered, but it is a starting point and not a verdict.
Match the Mix to Your Comfort With Swings
Consider how you would feel and what you would do if your balance fell 20% or more. If you would sell in a panic, a lower stock allocation may protect you from your own reactions. The best allocation is one you can hold through bad years.
Common Mistakes to Avoid
Most TSP problems are not about picking the wrong fund. They are about habits. Watching for these patterns can save you years of drift.
Leaving Everything in the Default
A default is a starting point, not a plan. If you have never reviewed your allocation, it may no longer match your timeline or your goals. A yearly check takes less than an hour.
Chasing Last Year’s Winner
Moving money into whichever fund just performed best is a common instinct, and the 2024 and 2026 results above show why it can backfire. Funds rotate in leadership, and by the time a trend is obvious, it may be ending.
Forgetting That There Are Two Settings
Your TSP has one setting for new contributions and another for your existing balance. Changing one does not change the other. Many people update their contribution allocation and leave the existing balance untouched, or the reverse. Check both.
Over-Concentrating
Putting everything in one fund, whether the G fund for safety or a stock fund for growth, concentrates risk. A balance of several funds, or an L fund that does the balancing, spreads it.
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The Puerto Rico Angle
Federal employees and retirees in Puerto Rico face the same fund choices as everyone else, but the surrounding rules can differ. The TSP is a federal plan, and how withdrawals are taxed for Puerto Rico residents is a separate question that deserves its own review.
Coordinate the TSP With the Rest of Your Plan
Your TSP sits next to a pension, Social Security, perhaps an IRA and possibly a spouse’s accounts. How much risk to take in the TSP depends on what else you own. A thoughtful federal employee retirement in Puerto Rico plan looks at all these pieces together, so that the TSP is chosen for its role, not in isolation.
Think About Withdrawals Early
The mix that serves you at 45 may not serve you at 65, when you start taking money out. Planning how and when you will withdraw affects which funds you want to hold as retirement approaches. Taxes and timing both matter, and the rules for Puerto Rico residents should be confirmed with a qualified professional.
Risk Is More Than Market Risk
Managing a TSP balance is one part of risk management in Puerto Rico, which also includes insurance, emergency savings, health costs and the possibility of an interrupted career. A plan that handles only the market leaves the other risks unaddressed.
A Simple Review You Can Do This Month
You do not need to become an investment expert. A short review, repeated once a year, goes a long way. Here is a simple routine.
Four Steps
Take about an hour and work through these steps with your latest statement.
- Write down your current allocation for contributions and for your existing balance.
- Note when you expect to start withdrawing money.
- Compare your mix with your timeline and your comfort with swings.
- Decide whether to change the mix, and if so, whether to do it gradually.
When to Get Help
If your situation involves a spouse’s accounts, a pension decision, a rollover or a move, a second opinion can help. A financial investment advisor in Puerto Rico who understands federal benefits can look at the TSP alongside everything else, instead of treating it as a separate puzzle.
Conclusion
The TSP menu looks complicated until you see its logic. The G fund protects, the F fund adds bond income, the C, S and I funds provide growth across large, small and international companies, and the L funds blend all of these on a schedule. Each has a job, a risk and a place.
The recent numbers carry a lasting lesson. Leadership among the funds changes often, and a choice built on your timeline, your pension and your comfort with risk is more durable than a choice built on last year’s winner. Review both of your settings, write down your reasoning and revisit it annually.
If you would like help fitting the TSP into your full retirement picture, JLA Financial Planning provides retirement planning services in Puerto Rico for federal employees, retirees and families.
Disclaimer: This article is for educational purposes only and does not constitute individualized financial, investment, tax, or legal advice. Past performance does not guarantee future results, and all investing involves risk, including possible loss of principal. Fund descriptions, indexes and returns change over time and should be confirmed on the official TSP website. Examples are illustrative.
