Company: KNSL
Filing Date: 2025-05-08
Form Type: DEFA14A
Source: 0001669162-25-000033
Chunk: 0

Company: Kinsale Capital Group, Inc.
Filing Date: 2025-05-08
Form: DEFA14A
Chunk 0
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### UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549

#### SCHEDULE 14A
<div align='center'>Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934</div>

| Filed by the Registrant☒                                                 |     |                                                                                 |
| Filed by a Party other than the Registrant ☐                             |     |                                                                                 |
| Check the appropriate box:                                               |     |                                                                                 |
| ☐                                                                        |     | Preliminary Proxy Statement                                                     |
| ☐                                                                        |     | Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) |
| ☐                                                                        |     | Definitive Proxy Statement                                                      |
| ☒                                                                        |     | Definitive Additional Materials                                                 |
| ☐                                                                        |     | Soliciting Material Pursuant to §240.14a-12                                     |
| Kinsale Capital Group, Inc.                                              |     |                                                                                 |
| (Name of Registrant as Specified in Its Charter)                         |     |                                                                                 |
| (Name of Person(s) Filing Proxy Statement, if other than the Registrant) |     |                                                                                 |

Payment of Filing Fee (Check all boxes that apply):

| ☒ |     | No fee required                                                                                     |
| ☐ |     | Fee paid previously with preliminary materials                                                      |
| ☐ |     | Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11 |

#### 2035 Maywill Street

#### Suite 100

#### Richmond, VA 23230
May 8, 2025

Dear Stockholder:

We are providing additional information and context on our proposal to approve the Kinsale Capital Group, Inc. 2025 Omnibus Incentive Plan (the “Plan”) at our 2025 Annual Meeting of Stockholders. If the Plan is approved by our stockholders, no further awards will be issued under the Kinsale Capital Group, Inc. 2016 Omnibus Incentive Plan (the “2016 Plan”) on or following the date the Plan is approved by our stockholders and the shares remaining available for grant of future awards under the 2016 Plan will not carry forward to the Plan. In addition, any shares granted under the 2016 Plan on or following March 27, 2025 will reduce the