MFS Municipal Income Fund
Actively managed U.S. bond fund
As of its 2026 Q2 report, MFS Municipal Income Fund held 2,343 positions with $7.18B in net assets. Its ten largest holdings made up 5.6% of the fund. The MFIAX share class costs 0.76% a year. Over the 12 months to May 2026, MFIAX returned 7.2%, with dividends reinvested. In 2026 Q2 it added 91 new positions and exited 40.
The funds investment objective is to seek total return with an emphasis on income exempt from U.S. federal income tax, but also considering capital appreciation.
The fund invests primarily in municipal bonds selected through fundamental analysis of individual instruments and issuers, seeking tax-exempt income with capital appreciation. At least 80% of assets go into securities whose interest is exempt from U.S. federal income tax, though the fund may hold below-investment-grade debt and can concentrate significantly in a single state or project type. Because the fund may invest 25% or more in similar-purpose municipal instruments and a substantial portion in issuers within one or few states, concentration risk applies to both project type and geographic location.
What you own
| Company | Weight | Value | Shares |
|---|---|---|---|
MFS Institutional Money Market Portfolio | 1.89% | $135.46M | — |
Black Belt Energy Gas District 5.00% · due 2034-12-01 | 0.52% | $37.05M | — |
Texas Municipal Gas Acquisition & Supply Corp. IV 5.50% floating · due 2054-01-01 | 0.45% | $32.53M | — |
Princeton Independent School District 5.25% · due 2055-02-15 | 0.42% | $30.18M | — |
New York Transportation Development Corp. 5.25% · due 2060-06-30 | 0.41% | $29.64M | — |
New York Transportation Development Corp. 5.13% · due 2060-06-30 | 0.41% | $29.57M | — |
New Hampshire Business Finance Authority 5.88% · due 2038-12-15 | 0.41% | $29.06M | — |
California Community Choice Financing Authority 5.25% floating · due 2054-01-01 | 0.39% | $27.79M | — |
Black Belt Energy Gas District 5.00% · due 2036-06-01 | 0.35% | $25.49M | — |
Black Belt Energy Gas District 5.50% floating · due 2054-10-01 | 0.35% | $25.08M | — |
The 200 largest of 2,343 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 | 95.98% |
| Cash & short-term | 1.99% |
| Securitized | 1.07% |
How it has done
MFIAX share class · total returns with dividends reinvested
Volatility over the last 12 months: 4.25%. Past returns are a record, not a forecast.
Jun 2026 has been filed since the trailing figures were struck, so it is 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 7 share classes hold the same portfolio
| Share class | Expense ratio | 1 year | 3 years | 5 years | Worst fall |
|---|---|---|---|---|---|
| 0.76% | +7.21% | +13.61% | +4.04% | -6.25% | |
| 1.51% | +6.41% | +11.11% | +0.24% | -6.30% | |
| 1.51% | +6.39% | +11.10% | +0.30% | -6.39% | |
| 0.51% | +7.48% | +14.49% | +5.40% | -6.18% | |
| 1.26% | +6.67% | +11.93% | +1.50% | -6.35% | |
| 0.51% | +7.47% | +14.45% | +5.30% | -6.19% | |
| 0.44% | +7.56% | +14.73% | +5.85% | -6.19% |
These classes hold the same portfolio, so the 5.61pp spread over 5 years is the cost difference between them — roughly 1.12pp a year — not a difference in what they own.
Fees & fund details
MFS Municipal 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
- Mixed credit
- Rate sensitivity
- Intermediate duration
- Expense ratio, by class
- 0.44% – 1.51%· MFIAX 0.76%
- Portfolio turnover
- 9.00% a year · as of 2025 Q3
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.
91 new· the largest 6
40 exited· the largest 8
Debt profile
What this fund holds — value-weighted across its bond and securitized long positions · as of 2026-06-30
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 | 85.5% |
| Floating rate | 12.2% |
| Zero-coupon or unclassified | 2.4% |
Share of the fund's debt value in each maturity band, shortest first.
| <1y | 0.5% |
| 1-3y | 1.6% |
| 3-5y | 1.5% |
| 5-10y | 10.7% |
| 10y+ | 85.6% |
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.
| Investment grade | +5.79 yr |
| High yield | +1.41 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 | 0.04 yr | 1% |
| 1 yr | 0.31 yr | 5% |
| 5 yr | 1.50 yr | 22% |
| 10 yr | 3.29 yr | 49% |
| 30 yr | 1.53 yr | 23% |
| 3 mo | 0.02 yr | 0% |
| 1 yr | 0.35 yr | 5% |
| 5 yr | 1.63 yr | 23% |
| 10 yr | 3.52 yr | 49% |
| 30 yr | 1.69 yr | 24% |
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 | +0.04 | +0.01 | +0.01 | $8.8k | $4.2k |
| 1 yr | +0.31 | +0.26 | +0.09 | $185.9k | $61.9k |
| 5 yr | +1.50 | +1.30 | +0.32 | $935.4k | $233.1k |
| 10 yr | +3.29 | +2.87 | +0.64 | $2.06m | $462.7k |
| 30 yr | +1.53 | +1.35 | +0.35 | $968.1k | $248.4k |
Dollar change per 1bp of spread movement, as filed and sign-anchored. A blank cell was not filed; a zero was.
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