MIOBX Performance — MFS Income Fund, Class B
Data updated: 2026-09-28
MIOBX returned −0.76% year to date and +2.04% over one year to Jul 2026. Annualised returns are +3.64% over 3 years and −0.52% over 5 years. The fund trailed its Intermediate Core Bond category average: $100 invested three years ago grew to $111, against $113 for the category, and to $102 over one year, against $103. Volatility over the past three years was 5.45% a year. In the 12 months to Jul 2026 the fund took in a net $1.6B, and assets reached $8.32B.
MIOBX Growth of $100
What $100 invested in MFS Income Fund grew to, compounded from monthly returns reported on SEC Form N-PORT, against the Intermediate Core Bond category average over the same months.
| Period | MIOBX | Category average |
|---|---|---|
| 1 year (Aug 2025 – Jul 2026) | $102 | $103 |
| 3 years (Aug 2023 – Jul 2026) | $111 | $113 |
| 5 years (Aug 2021 – Jul 2026) | $97 | $100 |
| Since data start (Aug 2019 – Jul 2026) | $108 | $110 |
MIOBX Trailing Returns
Total returns to Jul 2026, from SEC N-PORT.
| Period | Total return |
|---|---|
| YTD | −0.76% |
| 1 year | +2.04% |
| 3 years (annualised) | +3.64% |
| 5 years (annualised) | −0.52% |
MIOBX Annual Returns
Calendar-year total returns of MFS Income Fund, compounded from monthly SEC N-PORT returns. Partial years show the months covered.
| Year | Total return |
|---|---|
| 2026 (Jan–Jul) | −0.76% |
| 2025 | +6.57% |
| 2024 | +1.85% |
| 2023 | +6.67% |
| 2022 | −14.19% |
| 2021 | −1.06% |
| 2020 | +8.70% |
| 2019 (Aug–Dec) | +2.00% |
MIOBX Monthly Returns
Monthly total returns as reported on SEC Form N-PORT.
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2026 | +0.1% | +1.3% | −1.8% | +0.3% | +0.3% | +0.3% | −1.4% | — | — | — | — | — |
| 2025 | +0.7% | +1.9% | −0.2% | −0.2% | −0.2% | +1.5% | 0.0% | +1.0% | +1.2% | +0.3% | +0.7% | −0.4% |
| 2024 | 0.0% | −1.2% | +1.0% | −2.4% | +1.6% | +0.9% | +2.1% | +1.4% | +1.4% | −2.0% | +0.9% | −1.7% |
| 2023 | +3.8% | −2.5% | +2.0% | +0.7% | −1.3% | +0.2% | +0.5% | −0.8% | −2.4% | −1.8% | +4.7% | +3.8% |
| 2022 | −2.4% | −1.4% | −2.3% | −3.9% | 0.0% | −2.6% | +2.5% | −2.7% | −4.1% | −1.2% | +3.6% | −0.4% |
| 2021 | −0.4% | −1.4% | −1.1% | +0.9% | +0.3% | +1.1% | +0.8% | 0.0% | −1.0% | 0.0% | −0.2% | +0.1% |
| 2020 | +2.1% | +1.2% | −7.5% | +3.8% | +2.3% | +1.9% | +2.9% | −0.4% | −0.3% | −0.1% | +2.3% | +0.6% |
| 2019 | — | — | — | — | — | — | — | +2.3% | −0.4% | +0.2% | −0.1% | 0.0% |
MIOBX Risk
Risk measures from monthly returns over Aug 2023 – Jul 2026.
- 3-year volatility (annualised): 5.45%
- 3-year Sharpe ratio: -0.16 (vs 4.5% risk-free rate)
- Best month: +4.72% (Nov 2023)
- Worst month: −2.40% (Sep 2023)
MIOBX Fund Flows
Monthly money in and out of MFS Income Fund, from SEC Form N-PORT.
- 12-month net flow: $1.6B
- 12-month gross sales (incl. reinvestments): $3.7B
- Sales ÷ redemptions: 1.76×
| Month | Sales | Redemptions | Net flow |
|---|---|---|---|
| Jul 2026 | $273.4M | $223.6M | $49.7M |
| Jun 2026 | $266.1M | $170.7M | $95.4M |
| May 2026 | $277.8M | $163.0M | $114.8M |
| Apr 2026 | $289.0M | $177.1M | $111.9M |
| Mar 2026 | $355.0M | $309.3M | $45.7M |
| Feb 2026 | $346.8M | $186.4M | $160.4M |
| Jan 2026 | $344.5M | $211.6M | $132.9M |
| Dec 2025 | $284.4M | $120.8M | $163.6M |
| Nov 2025 | $301.4M | $118.8M | $182.6M |
| Oct 2025 | $371.3M | $166.1M | $205.2M |
| Sep 2025 | $289.6M | $142.0M | $147.6M |
| Aug 2025 | $305.0M | $120.6M | $184.5M |
MIOBX Assets Under Management
Net assets of MFS Income Fund by report date, from SEC N-PORT filings.
| Report date | Net assets |
|---|---|
| 2026-07-31 | $8.32B |
| 2026-04-30 | $8.20B |
| 2026-01-31 | $7.98B |
| 2025-10-31 | $7.54B |
| 2025-07-31 | $6.89B |
| 2025-04-30 | $6.54B |
| 2025-01-31 | $6.03B |
| 2024-10-31 | $5.64B |
| 2024-07-31 | $5.07B |
| 2024-04-30 | $4.46B |
| 2024-01-31 | $3.79B |
| 2023-10-31 | $2.69B |
For information only. Not investment advice: figures are as reported in SEC filings and may contain errors or be out of date. Past performance does not guarantee future results.