Company: AIZ
Filing Date: 2025-08-15
Form Type: 424B5
Source: 0001193125-25-181851
Chunk: 12

Company: ASSURANT, INC.
Filing Date: 2025-08-15
Form: 424B5
Chunk 12
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We intend to use the net proceeds from this offering to redeem all of the
$175.0 million outstanding aggregate principal amount of our 2026 Notes, to pay related premiums, fees and expenses and for general corporate purposes. Prior to such application of the proceeds described above, we may hold the proceeds in cash,
invest the proceeds, repay short-term indebtedness or otherwise utilize such proceeds.

This prospectus supplement does not constitute a
notice of redemption for the 2026 Notes, which will be made in accordance with the indenture governing the 2026 Notes.

S-9

CAPITALIZATION The following table sets forth our consolidated capitalization at June 30, 2025:

| • |     | on an actual basis; and |

| • |     | on an as adjusted basis to give effect to the consummation of this offering and the application of the net                                                                                   
 proceeds from this offering to redeem all of our 2026 Notes as described in “Use of Proceeds,” other than any fees or expenses incurred in connection with the redemption of the 2026 Notes. |

|                                                                                                  |     | As of June 30, 2025      |         |   |     |             |         |   |
|:-------------------------------------------------------------------------------------------------|:----|:-------------------------|--------:|:--|:----|:------------|--------:|:--|
|                                                                                                  |     | Actual                   |         |   |     | As Adjusted |         |   |
|                                                                                                  |     | -in millions, except per 
 share amounts            |         |   |     |             |         |   |
| Cash and cash equivalents(1)(2)                                                                  |     | $                        | 1,486.7 |   |     | $           | 1,604.1 |   |
| Debt outstanding                                                                                 |     |                          |         |   |     |             |         |   |
| 6.10% Senior Notes due February                                                                  
 2026(3)                                                                                          |     |                          |   174.6 |   |     |             |       — |   |
| 4.90% Senior Notes due March 2028                                                                |     |                          |   298.8 |   |     |             |   298.8 |   |
| 3.70% Senior Notes due February 2030                                                             |     |                          |   348.3 |   |     |             |   348.3