Fund Evaluator:
MFS Municipal Income A1 (MMIDX)
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Best Performing in Muni National Long Over the Last Year
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Fund Details
MFS Municipal Income A1 Overview
MFS Municipal Income A1 (MMIDX) is an actively managed Municipal Bond Muni National Long fund. MFS launched the fund in 2007.
The investment seeks total return with an emphasis on income exempt from federal income tax, but also considering capital appreciation. MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests the fund’s assets primarily in municipal instruments. The fund invests normally at least 80% of its net assets in securities and other investments, the interest on which is exempt from U.S. federal income tax. It may invest 25% or more of its total assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water, or sewers.
About MFS Municipal Income A1 (MMIDX)
There are 2 members of the management team with an average tenure of 7.72 years: Jason Kosty (2015), Megan Poplowski (2022). Management tenure is more important for actively managed funds than passive index funds.
The fund has 1 primary benchmark: Bloomberg Municipal TR USD index with a weighting of 100%. MFS Municipal Income A1 has 2343 securities in its portfolio. The top 10 holdings constitute 4.1% of the fund’s assets. The fund meets the SEC requirement of being classified as a diversified fund. The fund is not considered to have an ESG focus with its investment selection and management.
MFS Municipal Income A1 is part of the Fixed Income global asset class and is within the Municipal Bond fund group. MFS Municipal Income A1 has 1.3% of its portfolio invested in foreign issues. The overall assets allocated to domestic stock is 0.0%. There is 0.0% allocated to foreign stock, and 0.0% is allocated to preferred stocks. The bond allocation as a percentage of total assets is 97.8% (96.5% domestic bond, 1.3% foreign bond and 0.0% convertible bond). MFS Municipal Income A1 has 2.2% of the portfolio in cash.
Assets Under Management
The fund has $195 million in total assets, which is below the $1 billion average for the Muni National Long category. Normally, lower assets under management translates to higher average expense ratios, and greater total assets are desired. However, for some investment categories, such as small-cap investing, it may be difficult for the manager to fully employ the desired active strategy if assets grow too large or too quickly.
MMIDX Performance and Fees
The expense ratio measures how much of a fund’s assets are used for administrative expenses and operating expenses, including adviser fees and fees for the transfer agent and custodial services. The MFS Municipal Income A1 expense ratio is average compared to funds in the Muni National Long category. MFS Municipal Income A1 has an expense ratio of 0.54%, which is 31% lower than its category average, making the fund expense ratio grade a B. While it is difficult to predict returns, it is known that high annual expense ratios reduce your rate of return, and excessive fees are difficult to overcome. Active management normally comes with higher expense ratios than passive index management. Certain investment categories such as small company and foreign also normally have higher expense ratios. It is best to compare fund expense ratios against the category averages for meaningful assessments.
High portfolio turnover can translate to higher expenses and lower aftertax returns. MFS Municipal Income A1 has a portfolio turnover rate of 12%, indicating that holds its assets around 0.1 years. By way of comparison, the average portfolio turnover is 38% for the Muni National Long category.
Recently, in the month of July 2026, MFS Municipal Income A1 returned -1.7%, which earned it a grade of B, as the Muni National Long category had an average return of -1.9%. The letter grades of A, B, C, D and F are based upon relative rankings within the investment category. A grade of A, for example, would indicate that the return is in the highest 20% for that time period compared to all funds in that category.
MFS Municipal Income A1 has a trailing yield of 4.03%, which is above the 3.72% category average. The fund normally distributes its income monthly and its capital gains annually.
It’s natural to seek the best-performing investments, but you must consider the relationship between risk and return and the impact of costs and taxes on your realized returns.
MFS Municipal Income A1 Grades
Year to date, the fund has returned 1.1%, 0.2 percentage points better than the category, which translates into a grade of B. The fund has returned 6.7% over the past year (grade of B), 4.0% over the past three years (grade of A) and 0.6% per year over the past five years (grade of A) and 2.3% per year over the past 10 years (grade of A).
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MMIDX Trailing NAV Total Returns Data as of 7/31/26
| Last Month |
Last Quarter |
Ann'l. 1Yr |
Ann'l. 3Yr |
Ann'l. 5Yr |
Ann'l. 10Yr |
|
| MMIDX Return (NAV) | -1.7% | -0.1% | 6.7% | 4.0% | 0.6% | 2.3% |
| MMIDX Grade | B | B | B | A | A | A |
| +/- Category | 0.1% | 0.2% | 0.4% | 0.7% | 0.6% | 0.6% |
| Muni National Long Avg | -1.9% | -0.3% | 6.3% | 3.2% | 0.0% | 1.8% |
| MMIDX Tax Cost Ratio | na | na | 0.0% | 0.0% | 0.0% | 0.0% |
MMIDX Annual NAV Total ReturnsData as of 7/31/26
| 2026 | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | |
| MMIDX Return (NAV) | 1.1% | 3.6% | 3.5% | 7.0% | -10.8% | 3.3% | 4.4% | 8.3% | 1.4% | 6.0% | 1.3% |
| MMIDX Grade | B | B | A | C | C | B | D | B | A | B | A |
| +/- Category | 0.2% | 0.6% | 1.1% | 0.1% | 0.8% | 0.4% | -0.3% | 0.2% | 0.7% | 0.2% | 1.1% |
| Muni National Long Avg | 0.9% | 3.0% | 2.5% | 6.8% | -11.6% | 2.8% | 4.7% | 8.1% | 0.7% | 5.8% | 0.2% |
| Risk Measures | |
| Standard Deviation: | 6.5% |
| Total Risk Index: | 0.53 - Below Average |
| Category Risk Index: | 0.99 - Above Average |
| Category Risk Grade: | D (63% Rank) |
| Beta: | 1.11 |
| R-Squared: | 97% |
| Leveraged Fund: | No |
| Inverse Fund: | No |
| Portfolio Characteristics | |
| Equity Investment Style: | na |
| Bond Investment Style: | na |
| Yield: | 4.0% |
| Dividend Distribution: | Monthly |
| Cap Gains Distribution: | Annually |
| Total Assets: | $7066 Mil |
| Fund Total Assets: | $ 196 Mil |
| Share Class Type: | A |
| Portfolio Turnover: | 12% |
Management Team
| Number of Managers: 2 | |||
| Longest Tenure: 11.0 years | |||
| Average Tenure: 7.7 years | |||
| Managers (Year): Kosty Jason (2015), Poplowski Megan (2022) | |||
Portfolio Composition (as of 6/30/26)
| # of Holdings: | 2343 |
| % in Top 10 Holdings: | 4.1% |
| Fund is Non-Diversified: | No |
| % in Foreign Issues: | 1.3% |
Portfolio Allocation |
|
| Domestic Stock: | 0.0% |
| Foreign Stock: | 0.0% |
| Preferred Stock: | 0.0% |
| Domestic Bond: | 96.5% |
| Foreign Bond: | 1.3% |
| Convertible Bond: | 0.0% |
| Other: | 0.0% |
| Cash: | 2.2% |
Purchase Information
| Fund Family: | MFS |
| Phone Number: | 800-225-2606 |
| Website: | http://www.mfs.com |
| Status: | Closed |
| Inception Date: | June 25, 2007 |
| Min. Initial Purchase: | $1,000 |
| Min. Initial IRA Purchase: | $ 250 |
| True No-Load: | No |
| Front Load Maximum: | 4.25% |
| Deferred Charge Maximum: | 0.00% |
| Redemption Charge Maximum: | 0.00% |
| 12b-1 Fee: | na |
Expenses and Fees | |
| Expense Ratio (%): | 0.54% ( Rating : Avg ) |
| Category Average Expense Ratio (%): | 0.78% |
| Share Class: | MFS Municipal Income B |
| Min. Subsequent Purchase: | $ 50 |
| Min. Subsequent IRA Purchase: | $ 0 |
