MFBKX Performance — MFS Corporate Bond Fund, Class R6
Data updated: 2026-09-28
MFBKX returned −0.57% year to date and +2.71% over one year to Jul 2026. Annualised returns are +4.96% over 3 years and −0.04% over 5 years. The fund trailed its Intermediate Corporate Bond category average: $100 invested three years ago grew to $116, against $116 for the category, and to $103 over one year, against $103. Volatility over the past three years was 6.26% a year. In the 12 months to Jul 2026 the fund lost a net $95.3M, and assets reached $4.36B.
MFBKX Growth of $100
What $100 invested in MFS Corporate Bond Fund grew to, compounded from monthly returns reported on SEC Form N-PORT, against the Intermediate Corporate Bond category average over the same months.
| Period | MFBKX | Category average |
|---|---|---|
| 1 year (Aug 2025 – Jul 2026) | $103 | $103 |
| 3 years (Aug 2023 – Jul 2026) | $116 | $116 |
| 5 years (Aug 2021 – Jul 2026) | $100 | $103 |
| Since data start (Aug 2019 – Jul 2026) | $115 | $116 |
MFBKX Trailing Returns
Total returns to Jul 2026, from SEC N-PORT.
| Period | Total return |
|---|---|
| YTD | −0.57% |
| 1 year | +2.71% |
| 3 years (annualised) | +4.96% |
| 5 years (annualised) | −0.04% |
MFBKX Annual Returns
Calendar-year total returns of MFS Corporate Bond Fund, compounded from monthly SEC N-PORT returns. Partial years show the months covered.
| Year | Total return |
|---|---|
| 2026 (Jan–Jul) | −0.57% |
| 2025 | +7.79% |
| 2024 | +3.05% |
| 2023 | +9.31% |
| 2022 | −16.34% |
| 2021 | −1.19% |
| 2020 | +11.36% |
| 2019 (Aug–Dec) | +3.48% |
MFBKX 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 | +0.4% | +1.0% | −1.9% | +0.6% | +0.7% | +0.2% | −1.6% | — | — | — | — | — |
| 2025 | +0.7% | +2.1% | −0.4% | −0.2% | +0.1% | +2.0% | +0.1% | +1.1% | +1.5% | +0.4% | +0.6% | −0.2% |
| 2024 | +0.1% | −1.3% | +1.3% | −2.4% | +2.0% | +0.7% | +2.3% | +1.6% | +1.8% | −2.3% | +1.1% | −1.8% |
| 2023 | +4.5% | −3.0% | +2.8% | +0.7% | −1.4% | +0.5% | +0.4% | −0.7% | −2.7% | −1.9% | +5.9% | +4.4% |
| 2022 | −3.4% | −2.0% | −2.4% | −5.5% | +0.8% | −3.7% | +3.6% | −2.8% | −5.2% | −0.6% | +5.0% | −0.6% |
| 2021 | −1.4% | −2.0% | −1.4% | +1.2% | +0.4% | +1.8% | +1.3% | −0.1% | −1.0% | 0.0% | −0.4% | +0.3% |
| 2020 | +2.3% | +1.2% | −6.8% | +5.9% | +1.9% | +1.9% | +3.6% | −1.2% | −0.3% | −0.1% | +2.8% | +0.4% |
| 2019 | — | — | — | — | — | — | — | +3.1% | −0.6% | +0.5% | +0.2% | +0.2% |
MFBKX Risk
Risk measures from monthly returns over Aug 2023 – Jul 2026.
- 3-year volatility (annualised): 6.26%
- 3-year Sharpe ratio: 0.07 (vs 4.5% risk-free rate)
- Best month: +5.88% (Nov 2023)
- Worst month: −2.72% (Sep 2023)
MFBKX Fund Flows
Monthly money in and out of MFS Corporate Bond Fund, from SEC Form N-PORT.
- 12-month net flow: −$95.3M
- 12-month gross sales (incl. reinvestments): $1.1B
- Sales ÷ redemptions: 0.92×
| Month | Sales | Redemptions | Net flow |
|---|---|---|---|
| Jul 2026 | $101.1M | $111.8M | −$10.7M |
| Jun 2026 | $180.8M | $91.7M | $89.1M |
| May 2026 | $64.6M | $89.8M | −$25.2M |
| Apr 2026 | $76.5M | $116.8M | −$40.4M |
| Mar 2026 | $74.2M | $109.6M | −$35.4M |
| Feb 2026 | $86.2M | $85.2M | $982K |
| Jan 2026 | $85.8M | $96.3M | −$10.4M |
| Dec 2025 | $79.2M | $131.8M | −$52.6M |
| Nov 2025 | $77.3M | $74.4M | $2.9M |
| Oct 2025 | $105.6M | $111.0M | −$5.4M |
| Sep 2025 | $80.7M | $84.2M | −$3.5M |
| Aug 2025 | $71.5M | $76.4M | −$4.8M |
MFBKX Assets Under Management
Net assets of MFS Corporate Bond Fund by report date, from SEC N-PORT filings.
| Report date | Net assets |
|---|---|
| 2026-07-31 | $4.36B |
| 2026-04-30 | $4.38B |
| 2026-01-31 | $4.52B |
| 2025-10-31 | $4.61B |
| 2025-07-31 | $4.54B |
| 2025-04-30 | $4.52B |
| 2025-01-31 | $4.60B |
| 2024-10-31 | $4.64B |
| 2024-07-31 | $4.51B |
| 2024-04-30 | $4.34B |
| 2024-01-31 | $4.44B |
| 2023-10-31 | $3.99B |
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.