Company: CALX
Filing Date: 2025-07-22
Form Type: S-8
Source: 0001406666-25-000036
Chunk: 3

Company: CALIX, INC
Filing Date: 2025-07-22
Form: S-8
Chunk 3
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) (collectively with the Stock Purchase and Matching Plan Original Registration Statement, the Stock Purchase and Matching Plan 2018 Registration Statement, the Stock Purchase and Matching Plan 2020 Registration Statement, the Stock Purchase and Matching Plan 2021 Registration Statement and the Stock Purchase and Matching Plan 2022 Registration Statement, the “Stock Purchase and Matching Plan Prior Registration Statements”), the Registrant registered an additional 1,200,000 shares of Common Stock issuable under the Stock Purchase and Matching Plan.

Pursuant to Instruction E of Form S-8, the contents of the 2019 Plan Prior Registration Statements and the Stock Purchase and Matching Plan Prior Registration Statements are incorporated by reference in this registration statement on Form S-8.

# PART I
<div align='center'>INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS</div>

The documents containing the information specified in Part I of Form S-8 will be sent or given to participants as specified by Rule 428(b)(1) of the Securities Act of 1933, as amended (the “Securities Act”). These documents and the documents incorporated by reference into this Registration Statement pursuant to Item 3 of Part II of this Registration Statement, taken together, constitute a prospectus that meets the requirements of Section 10(a) of the Securities Act.

<div align='center'>3</div>

# PART II

### INFORMATION REQUIRED IN THE REGISTRATION STATEMENT
| Item 3. |     | Incorporation of Documents by Reference. |

The SEC allows us to incorporate by reference the information we file with it, which means that we can disclose important information to you by referring to those documents. The information incorporated by reference is an important part of this Registration Statement, and information that we file later with the SEC will automatically update and supersede this information. We incorporate by reference the following documents we have filed, or may file, with the SEC:

| (1) |     | OurAnnual Report on Form 10-K(File No. 001-34674) for the fiscal year ended December 31, 2024, filed with the SEC on February 21, 2025, including the information specifically incorporated by reference therein from ourdefinitive proxy statement on Schedule 14Afiled with the SEC on March 27, 2025;                               |
| (2) |     | Our Quarterly Reports on Form 10-Q (File No. 001-34674), filed with the SEC onApril 22, 202