MFS Municipal High Income Fund
Actively managed U.S. bond fund
As of its 2026 Q2 report, MFS Municipal High Income Fund held 2,039 positions with $5.40B in net assets. Its ten largest holdings made up 8.1% of the fund. The MMHYX share class costs 0.66% a year. Over the 12 months to May 2026, MMHYX returned 8.1%, with dividends reinvested. In 2026 Q3 it added 125 new positions and exited 25.
The funds investment objective is to seek total return with an emphasis on high income exempt from U.S. federal income tax, but also considering capital appreciation.
The fund invests primarily in municipal bonds selected through bottom-up fundamental analysis of individual issuers, with at least 80% of assets in federal tax-exempt securities. The fund may concentrate 25% or more of assets in similar project types such as education, healthcare, or utilities, and may invest significantly in a single state or small number of states. Because the fund may allocate up to 100% of assets to below-investment-grade municipal debt and concentrate holdings by geography and project type, performance depends heavily on the credit quality and performance of those concentrated positions.
What you own
| Company | Weight | Value | Shares |
|---|---|---|---|
MFS Institutional Money Market Portfolio | 2.37% | $128.18M | — |
Puerto Rico Sales Tax Financing Corp. Sales Tax Revenue 5.00% · due 2058-07-01 | 1.85% | $99.98M | — |
Berks County Municipal Authority (The) 5.00% · due 2039-06-30 | 0.59% | $31.78M | — |
Buckeye Tobacco Settlement Financing Authority 5.00% · due 2055-06-01 | 0.58% | $31.12M | — |
California Community Choice Financing Authority 5.25% floating · due 2054-01-01 | 0.50% | $26.99M | — |
New York Transportation Development Corp. 5.13% · due 2060-06-30 | 0.46% | $24.72M | — |
New Hampshire Business Finance Authority 5.88% · due 2038-12-15 | 0.45% | $24.29M | — |
City of Chicago IL 5.00% · due 2033-01-01 | 0.45% | $24.08M | — |
New York Transportation Development Corp. 5.25% · due 2060-06-30 | 0.44% | $23.61M | — |
Iowa Tobacco Settlement Authority 0.00% · due 2065-06-01 | 0.42% | $22.79M | — |
The 200 largest of 2,039 holdings, with the share counts as filed, open with a free account.
What the fund is made of
Percentages are of fund net assets. Rounding, liabilities and short positions can make totals differ from 100%.
| Bonds | 95.54% |
| Cash & short-term | 2.37% |
| Securitized | 0.79% |
How it has done
MMHYX share class · total returns with dividends reinvested
Volatility over the last 12 months: 4.60%. Past returns are a record, not a forecast.
Jun 2026 and Jul 2026 have been filed since the trailing figures were struck, so they are not in the table above or the curve — every figure here shares one cut-off, which is what makes them comparable with other funds.
The 5 share classes hold the same portfolio
| Share class | Expense ratio | 1 year | 3 years | 5 years | Worst fall |
|---|---|---|---|---|---|
| 0.66% | +8.13% | +18.19% | +5.70% | -6.67% | |
| 1.41% | +7.18% | +15.45% | +1.84% | -6.83% | |
| 1.66% | +6.90% | +14.53% | +0.37% | -6.90% | |
| 0.66% | +7.98% | +17.98% | +5.58% | -6.67% | |
| 0.57% | +8.19% | +18.26% | +6.05% | -6.79% |
These classes hold the same portfolio, so the 5.68pp spread over 5 years is the cost difference between them — roughly 1.14pp a year — not a difference in what they own.
Fees & fund details
MFS Municipal High Income Fund is an actively managed U.S. bond fund.
- Asset class
- Bonds
- Region
- United States
- Management
- Actively managed
- Fund type
- Open-end fund
- Credit quality
- High yield
- Rate sensitivity
- Intermediate duration
- Expense ratio, by class
- 0.57% – 1.66%· MMHYX 0.66%
- Portfolio turnover
- 9.00% a year · as of 2026 Q2
Net is what a holder pays after the adviser's contractual waiver; gross is before it. A waiver can expire.
Turnover is how much of the portfolio was replaced in a year.
Classified from what the fund holds, not from its name · 2026 Q2. The summary is a paraphrase of the prospectus; the objective is verbatim.
What changed this quarter
Positions that entered or left the fund since its previous filing. Positions that were only resized are not listed.
125 new· the largest 7
25 exited· the largest 7
Debt profile
What this fund holds — value-weighted across its bond and securitized long positions · as of 2026-04-30
Share of the fund's debt by how its coupon behaves — the fact that decides whether a rate move reaches this portfolio at all.
| Fixed rate | 87.5% |
| Floating rate | 9.0% |
| Zero-coupon or unclassified | 3.5% |
Share of the fund's debt value in each maturity band, shortest first.
| <1y | 0.5% |
| 1-3y | 1.6% |
| 3-5y | 1.9% |
| 5-10y | 7.8% |
| 10y+ | 88.2% |
These three overlap — one holding can be in arrears and paying in kind at once — so they are shown separately and never summed.
Risk profile
Interest-rate and credit-spread sensitivity, both in years · as of 2026Q2
More of this fund’s sensitivity sits in credit spreads than in interest rates — a rate rally that comes with a credit selloff works against it.
Where the loss would come from. The two shocks are the same size, so this is the balance of the fund's two sensitivities rather than a bet on one moving more.
| Credit spreads | 52% |
| Interest rates | 48% |
Filers report the impact of a 0.01% move only, so the total is our own scaling of that one number and overstates the loss on most bonds — read it as approximate, never as precise. The two sensitivities overlap rather than add up: they measure the same positions against different shocks, which is why the durations above are shown side by side and never summed.
Share of the fund's spread duration carried by each credit tier.
| High yield | +3.87 yr |
| Investment grade | +3.14 yr |
Share of duration at each point, shortest first. A positive figure loses value when spreads widen; a negative one offsets — a credit hedge.
| 3 mo | 0.02 yr | 0% |
| 1 yr | 0.31 yr | 5% |
| 5 yr | 1.32 yr | 20% |
| 10 yr | 3.11 yr | 48% |
| 30 yr | 1.76 yr | 27% |
| 3 mo | 0.02 yr | 0% |
| 1 yr | 0.37 yr | 5% |
| 5 yr | 1.41 yr | 20% |
| 10 yr | 3.33 yr | 47% |
| 30 yr | 1.89 yr | 27% |
The two bands measure the same positions against different shocks and do not add — a Treasury carries rate duration and no spread duration, a floating-rate credit the reverse. Rate tenors are also summed across every currency the fund discloses.
Show the numbers
| Tenor | Rate yrs | IG yrs | HY yrs | IG $/bp | HY $/bp |
|---|---|---|---|---|---|
| 3 mo | +0.02 | +0.01 | +0.02 | $3.4k | $8.2k |
| 1 yr | +0.31 | +0.12 | +0.25 | $64.9k | $133.4k |
| 5 yr | +1.32 | +0.61 | +0.79 | $331.4k | $428.6k |
| 10 yr | +3.11 | +1.49 | +1.83 | $807.9k | $989.3k |
| 30 yr | +1.76 | +0.91 | +0.98 | $491.9k | $532.3k |
Dollar change per 1bp of spread movement, as filed and sign-anchored. A blank cell was not filed; a zero was.
A newer credit-spread reading (2026Q3) is on file. This page holds one quarter across every figure on it, so that one appears here next quarter.
Understand how this fund fits with the rest.
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