What Is IUSB? iShares Core Universal USD Bond ETF
Last updated September 2026
Short answer
IUSB is iShares Core Universal USD Bond ETF, an ETF that tracks a broad index of US dollar-denominated investment-grade and select higher-yielding bonds at a 0.06% expense ratio. IUSB is a broad US bond fund with a deliberate extension. Where a standard aggregate fund holds only investment-grade debt, IUSB's universal mandate lets it also hold a measured allocation to high-yield corporates and emerging-market dollar debt. That is the 'plus' in core-plus, and it is why the fund yields about 4.21% at a cost of 0.06% while carrying slightly more credit risk than a pure aggregate index fund.
IUSB is issued by iShares and tracks a broad index of US dollar-denominated investment-grade and select higher-yielding bonds. It charges a 0.06% expense ratio, holds approximately $42.8B in assets under management, yields about 4.21%, and launched in 2014.
What core-plus actually adds
The standard US aggregate index covers Treasuries, agency mortgage-backed securities and investment-grade corporate bonds. It deliberately excludes anything rated below investment grade.
A universal or core-plus mandate widens that. The fund can hold some high-yield corporate debt and dollar-denominated emerging-market bonds, in modest proportions. The effect is a slightly higher yield and slightly more sensitivity to credit conditions, without turning the fund into a high-yield vehicle.
The practical question is whether you want that decision made inside your core bond holding or made explicitly by holding an aggregate fund plus a separate high-yield sleeve you can size yourself. Neither is wrong; the second gives you more control.
The two risks, in order
Interest rates come first. This is a broad, intermediate-duration bond fund, so when rates rise the value of bonds already held falls, and the fund can post a negative year with no issuer missing a payment. That mechanism catches out people who think of bonds as the safe part of a portfolio.
Credit comes second, and matters more here than in a pure aggregate fund because of the high-yield and emerging-market sleeves. In a genuine credit event those holdings fall hardest, and they fall at the same time equities do, which is precisely when you wanted your bonds to be helping.
IUSB holdings: top 10
Approximate weights as of August 2026. Each ticker links to its individual stock guide in Walnut.
| Rank | Ticker | Company | % of IUSB |
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How do I invest in IUSB?
There are three common ways to get IUSB exposure. Buy shares (or fractional shares) of IUSB directly at any major broker that lists it. Hold it as a core position and layer more concentrated ideas on top. Or build it into a thematic portfolio in Walnut, so IUSB sits alongside other holdings that express the same thesis, with target weights you can rebalance toward. IUSB trades like a stock during market hours, so you buy it the same way you would any listed share.
New to buying funds? See how to buy an ETF, step by step.
Is IUSB a good buy?
Whether IUSB is a good buy depends less on any single call and more on your time horizon and what you already hold: it tracks a broad index of US dollar-denominated investment-grade and select higher-yielding bonds, so the real question is whether you want that exposure in your mix and at what weight. We walk through valuation, concentration, and what would have to be true for it to outperform from here in is IUSB a buy?
The bottom line on IUSB
IUSB gives you a broad index of US dollar-denominated investment-grade and select higher-yielding bonds exposure in one ticker at a 0.06% expense ratio. Most investors use it as a core holding and layer more concentrated thematic portfolios on top.
More on IUSB
Whether IUSB is worth buying today depends more on your time horizon and what you already hold than on any single call. We walk through valuation, concentration, and what would have to be true for it to outperform from here in is IUSB a buy?
IUSB yields 4.21% as of August 2026, paid by passing through the dividends of its underlying holdings. For the payout schedule, history, and how the distributions are taxed, see IUSB dividend: yield and schedule.
New to funds like IUSB? Start with what an ETF is, then how to buy an ETF, or browse the full guide to ETF investing.
Wondering how IUSB fits the portfolio you already own? Walnut is an AI investing app that connects your brokerage read-only and answers questions like that about your actual holdings: overlap, concentration, and how each position tracks the S&P 500. Compare the best AI portfolio analyzers or see the best AI investing apps in 2026.
Investing in IUSB with AI
Connect the broker you already use and ask Walnut's AI how IUSB fits what you actually hold: what it overlaps with, what it leaves you exposed to, and how it has tracked the S&P 500. Read-only by default, and you approve anything before it reaches your broker.
FAQ
What is IUSB?
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IUSB is the iShares Core Total USD Bond Market ETF. It holds a broad range of US dollar-denominated bonds: Treasuries, agency mortgage-backed securities and investment-grade corporates, plus measured allocations to high-yield and emerging-market dollar debt. It charges 0.06%, holds about $42.8B, distributes roughly 4.21%, and launched in 2014.
What does core-plus mean?
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The core is the standard investment-grade US bond market. The plus is a modest allocation to things that market excludes, mainly high-yield corporate debt and dollar-denominated emerging-market bonds. It lifts the yield and adds credit sensitivity without making the fund a high-yield vehicle.
IUSB vs AGG: what is the difference?
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AGG tracks the standard US aggregate index, investment grade only. IUSB uses a broader universal mandate that also permits high-yield and emerging-market dollar bonds in small proportions. IUSB yields a little more and carries a little more credit risk. If you would rather size that risk yourself, holding AGG plus a separate high-yield sleeve gives you the control.
Can IUSB lose money?
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Yes, most often through interest rates rather than defaults. When rates rise, the fixed payments on bonds already held become less attractive and prices fall. The credit sleeves add a second route in a genuine downturn, when high-yield and emerging-market debt fall alongside equities.
Is IUSB a good single bond holding?
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It is designed to be one: broad, cheap at 0.06%, and covering most of the dollar bond market in a single ticker. The question to settle is whether you want the high-yield and emerging-market exposure bundled in or kept separate where you control the size.
How often does IUSB pay?
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Monthly, which is standard for bond funds because the underlying interest arrives on a rolling basis. The amount varies with prevailing rates and portfolio turnover rather than being fixed.
How is IUSB taxed?
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Distributions are interest income, generally taxed at ordinary rates rather than the lower qualified-dividend rates that apply to most stock dividends. The Treasury portion of the interest is typically exempt from state and local tax. Bond funds are often held inside tax-advantaged accounts for this reason. This is not tax advice.
Does IUSB protect a portfolio when stocks fall?
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Partly. Its Treasury and agency holdings tend to attract buyers when investors move to safety. Its high-yield and emerging-market sleeves do the opposite, falling with equities. The net effect is a cushion, and a slightly thinner one than a pure Treasury or aggregate fund would provide.
What is IUSB's expense ratio?
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IUSB has an expense ratio of 0.06% per year as of August 2026, charged by iShares and deducted from the fund's value rather than billed to you separately. On a $10,000 position that is roughly $6 a year. Fees compound over time, so on a long-term holding the expense ratio is one of the few return drivers you control. It is worth comparing against other funds that track a broad index of US dollar-denominated investment-grade and select higher-yielding bonds before you choose.
How do I compare IUSB to similar ETFs?
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Put a few fields side by side: the expense ratio (fees compound over decades), the index or strategy it tracks, the top holdings and how much they overlap with what you already own, the dividend yield, and the AUM, liquidity, and bid-ask spread that affect trading costs. For index funds, tracking error (how closely it follows its index) and tax efficiency matter too. IUSB's figures are above; the full method is in Walnut's guide on how to compare ETFs.
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Walnut is informational, not investment advice. Holdings weights and fund statistics on this page are approximations stamped to August 2026; verify current figures against iShares's fund page or your broker before investing.