MRBIX Performance — MFS Total Return Bond Fund, Class I
Data updated: 2026-09-28
MRBIX returned −0.37% year to date and +2.91% over one year to Jul 2026. Annualised returns are +4.35% over 3 years and +0.04% over 5 years. Against its Intermediate Core Bond category average the fund came out ahead over three years but behind over one: $100 invested three years ago grew to $114, against $113 for the category, and to $103 over one year, against $103. Volatility over the past three years was 5.60% a year. In the 12 months to Jul 2026 the fund took in a net $6.6M, and assets reached $8.09B.
MRBIX Growth of $100
What $100 invested in MFS Total Return Bond 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 | MRBIX | Category average |
|---|---|---|
| 1 year (Aug 2025 – Jul 2026) | $103 | $103 |
| 3 years (Aug 2023 – Jul 2026) | $114 | $113 |
| 5 years (Aug 2021 – Jul 2026) | $100 | $100 |
| Since data start (Aug 2019 – Jul 2026) | $112 | $110 |
MRBIX Trailing Returns
Total returns to Jul 2026, from SEC N-PORT.
| Period | Total return |
|---|---|
| YTD | −0.37% |
| 1 year | +2.91% |
| 3 years (annualised) | +4.35% |
| 5 years (annualised) | +0.04% |
MRBIX Annual Returns
Calendar-year total returns of MFS Total Return Bond Fund, compounded from monthly SEC N-PORT returns. Partial years show the months covered.
| Year | Total return |
|---|---|
| 2026 (Jan–Jul) | −0.37% |
| 2025 | +7.33% |
| 2024 | +2.44% |
| 2023 | +7.21% |
| 2022 | −13.91% |
| 2021 | −0.80% |
| 2020 | +8.84% |
| 2019 (Aug–Dec) | +2.16% |
MRBIX 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 | +0.2% | +1.6% | −1.7% | +0.2% | +0.3% | +0.2% | −1.2% | — | — | — | — | — |
| 2025 | +0.7% | +2.2% | −0.1% | +0.1% | −0.5% | +1.6% | −0.2% | +1.1% | +1.2% | +0.6% | +0.7% | −0.2% |
| 2024 | 0.0% | −1.2% | +1.0% | −2.4% | +1.7% | +1.1% | +2.3% | +1.5% | +1.4% | −2.2% | +1.1% | −1.6% |
| 2023 | +3.9% | −2.5% | +2.1% | +0.7% | −1.0% | 0.0% | +0.2% | −0.6% | −2.5% | −1.6% | +4.8% | +3.9% |
| 2022 | −2.3% | −1.3% | −2.4% | −3.9% | +0.2% | −2.3% | +2.6% | −2.8% | −4.3% | −1.2% | +3.7% | −0.5% |
| 2021 | −0.6% | −1.5% | −1.1% | +0.9% | +0.3% | +1.0% | +1.1% | −0.2% | −0.7% | 0.0% | 0.0% | 0.0% |
| 2020 | +2.1% | +1.4% | −4.6% | +3.1% | +1.7% | +1.5% | +2.4% | −0.5% | −0.2% | −0.1% | +1.8% | +0.4% |
| 2019 | — | — | — | — | — | — | — | +2.5% | −0.6% | +0.3% | 0.0% | 0.0% |
MRBIX Risk
Risk measures from monthly returns over Aug 2023 – Jul 2026.
- 3-year volatility (annualised): 5.60%
- 3-year Sharpe ratio: -0.03 (vs 4.5% risk-free rate)
- Best month: +4.79% (Nov 2023)
- Worst month: −2.54% (Sep 2023)
MRBIX Fund Flows
Monthly money in and out of MFS Total Return Bond Fund, from SEC Form N-PORT.
- 12-month net flow: $6.6M
- 12-month gross sales (incl. reinvestments): $1.7B
- Sales ÷ redemptions: 1.00×
| Month | Sales | Redemptions | Net flow |
|---|---|---|---|
| Jul 2026 | $178.6M | $147.9M | $30.8M |
| Jun 2026 | $121.2M | $145.2M | −$24.0M |
| May 2026 | $125.5M | $166.1M | −$40.6M |
| Apr 2026 | $123.2M | $144.0M | −$20.8M |
| Mar 2026 | $126.5M | $169.3M | −$42.8M |
| Feb 2026 | $158.2M | $109.4M | $48.8M |
| Jan 2026 | $155.6M | $136.1M | $19.5M |
| Dec 2025 | $134.8M | $130.3M | $4.5M |
| Nov 2025 | $157.0M | $147.2M | $9.7M |
| Oct 2025 | $154.3M | $139.2M | $15.1M |
| Sep 2025 | $117.8M | $116.5M | $1.3M |
| Aug 2025 | $113.0M | $107.8M | $5.2M |
MRBIX Assets Under Management
Net assets of MFS Total Return Bond Fund by report date, from SEC N-PORT filings.
| Report date | Net assets |
|---|---|
| 2026-07-31 | $8.09B |
| 2026-04-30 | $8.26B |
| 2026-01-31 | $8.35B |
| 2025-10-31 | $8.36B |
| 2025-07-31 | $8.19B |
| 2025-04-30 | $8.08B |
| 2025-01-31 | $8.17B |
| 2024-10-31 | $8.08B |
| 2024-07-31 | $7.89B |
| 2024-04-30 | $7.58B |
| 2024-01-31 | $7.65B |
| 2023-10-31 | $6.96B |
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.