MFIAX — MFS Municipal Income Fund
Data updated: 2026-08-25
MFIAX — MFS Municipal Income Fund. Long Municipal - National Bond · $7.18B AUM · 0.79% expense ratio. Holdings, fees, performance and SEC filings.
MFIAX Fund Overview
MFIAX — MFS Municipal Income Fund is a US mutual fund managed by Mfs Municipal Series Trust, categorised as Long Municipal - National Bond. ABC INVEST provides holdings, performance, costs, cashflows, risk data, prospectus documents and SEC filings, sourced from SEC filings.
- Type: US mutual fund
- Manager: Mfs Municipal Series Trust
- Category: Long Municipal - National Bond
- Assets under management: $7.18B
- 1-year return: 7.6%
- Ticker: MFIAX
- SEC CIK: 0000751656
- SEC series ID: S000002536
- Share class ID: C000006991
MFIAX Holdings
Top 10 holdings of MFS Municipal Income Fund by percentage of net assets, from the fund's latest SEC N-PORT filing.
| Holding | % of net assets |
|---|---|
| MFS Institutional Money Market Portfolio | 1.89% |
| Black Belt Energy Gas District | 0.52% |
| Texas Municipal Gas Acquisition & Supply Corp. IV | 0.45% |
| Princeton Independent School District | 0.42% |
| New York Transportation Development Corp. | 0.41% |
| New York Transportation Development Corp. | 0.41% |
| New Hampshire Business Finance Authority | 0.40% |
| California Community Choice Financing Authority | 0.39% |
| Black Belt Energy Gas District | 0.35% |
| Black Belt Energy Gas District | 0.35% |
MFIAX Portfolio Allocation
Asset-class allocation of MFS Municipal Income Fund by percentage of net assets, from the latest SEC N-PORT filing.
| Asset class | Allocation |
|---|---|
| Fixed Income | 96.0% |
| Cash & Equivalents | 2.0% |
| Securitized | 1.1% |
MFIAX Performance
Total returns for MFIAX (as of 2026-09-01), from SEC filings.
| Period | Total return |
|---|---|
| YTD | 2.7% |
| 1 year | 7.6% |
| 3 years (annualised) | 4.4% |
| 5 years (annualised) | 0.9% |
MFIAX Risk Information
Risk metrics for MFIAX, derived from monthly returns in SEC filings.
- 1-year volatility (annualised): 4.3%
MFIAX Costs and Fees
MFIAX costs about $79 per $10,000 invested per year in fund expenses.
- Net expense ratio: 0.79%
- Gross expense ratio: 0.80%
- Portfolio turnover: 12%
- Brokerage commissions: 0.00 bps of average net assets (SEC N-CEN)
MFIAX Cashflows
Over the 12 months to 2026-06, MFS Municipal Income Fund had net inflows of $1.11B, from monthly SEC N-PORT filings.
| Month | Net flow |
|---|---|
| 2026-06 | $40.66M |
| 2026-05 | $37.82M |
| 2026-04 | $20.36M |
| 2026-03 | $23.50M |
| 2026-02 | $63.82M |
| 2026-01 | $289.93M |
MFIAX Debt Constituents
Largest debt holdings of MFS Municipal Income Fund by percentage of net assets, from the latest SEC N-PORT filing.
| Debt holding | % of net assets |
|---|---|
| Black Belt Energy Gas District | 0.52% |
| Texas Municipal Gas Acquisition & Supply Corp. IV | 0.45% |
| Princeton Independent School District | 0.42% |
| New York Transportation Development Corp. | 0.41% |
| New York Transportation Development Corp. | 0.41% |
| New Hampshire Business Finance Authority | 0.40% |
| California Community Choice Financing Authority | 0.39% |
| Black Belt Energy Gas District | 0.35% |
| Black Belt Energy Gas District | 0.35% |
| New Hampshire Business Finance Authority | 0.35% |
MFIAX Prospectus and SEC Filings
Official MFS Municipal Income Fund filings on SEC EDGAR — prospectus, portfolio holdings and annual reports.
- Prospectus (485BPOS) — filed 2026-07-28
- Prospectus (485BPOS) — filed 2025-07-28
- Prospectus (485BPOS) — filed 2024-07-26
- Portfolio holdings (N-PORT) — filed 2026-08-25
- Portfolio holdings (N-PORT) — filed 2026-05-26
- Portfolio holdings (N-PORT) — filed 2026-02-25
- Annual census (N-CEN) — filed 2026-06-11
- Annual census (N-CEN) — filed 2025-06-11
Related Funds
Other Long Municipal - National Bond funds tracked on ABC INVEST:
Data Sources
ABC INVEST compiles this page from public filings made to the U.S. Securities and Exchange Commission (SEC) through EDGAR: portfolio holdings and monthly cashflows from Form N-PORT, expenses and returns from fund prospectuses (Form 485BPOS) and the SEC DERA Risk/Return Summary data sets, annual data from Form N-CEN, and shareholder reports from Form N-CSR.