As filed with the United States Securities and Exchange Commission on July 31, 2023

Registration No. 333-

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-8

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Casa Systems, Inc.

(Exact Name of Registrant as Specified in Its Charter)

Restricted Stock Unit Inducement Award

(Full title of the plan)

Edward Durkin

Interim Chief Executive Officer and Chief Financial Officer

Casa Systems, Inc.

100 Old River Road

Andover, Massachusetts 01810

(Name and address of agent for service)

(978) 688-6706

(Telephone number, including area code, of agent for service)

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.   ☐

EXPLANATORY NOTE

This Registration Statement on Form S-8 registers shares of common stock, par value $0.001 per share (the “Common Stock”), of Casa Systems, Inc. (the “Registrant”) issuable pursuant to the Inducement Award, as described below. To induce the individual listed below to accept employment with the Registrant, the Registrant granted the following equity award to such individual (the “Inducement Award”) on the date listed below:

The Inducement Award was approved by the Registrant’s Compensation Committee of the Board of Directors in compliance with and in reliance on Nasdaq Listing Rule 5635(c)(4). The Inducement Award was granted outside of the Registrant’s 2017 Stock Incentive Plan.

PART I

INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

The information specified in Part I of Form S-8 is omitted from this filing in accordance with the provisions of Rule 428 under the Securities Act of 1933, as amended (the “Securities Act”) and the introductory note to Part I of the Form S-8 instructions. The documents containing the information specified in Part I will be delivered to the person to whom the Inducement Award has been granted as required by Rule 428(b)(1) under the Securities Act.

PART II

INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

The following documents of the Registrant filed with the Commission are incorporated by reference in this Registration Statement as of their respective dates:

(a) the Registrant’s Annual Report on Form 10-K for the year ended December 31, 2022, filed with the Commission on March 15, 2023;

(b) the Registrant’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2023, filed with the SEC on May  9, 2023;

(c) the Registrant’s Definitive Proxy Statement on Schedule 14A, filed with the SEC on April 6, 2023, with respect to those portions that are incorporated by reference in our Annual Report on Form 10-K for the fiscal year ended December 31, 2022;

(d) the Registrant’s Current Reports on Form 8-K (in each case other than portions thereof furnished under Item 2.02 or Item 7.01 of Form 8-K and exhibits accompanying such reports related to such items) filed on January 31, 2023, March 14, 2023, May 9, 2023, June  16, 2023 and July 13, 2023; and

(e) the description of the Registrant’s Common Stock contained in the Registration Statement on Form 8-A filed with the Commission on December 12, 2017, together with any amendment thereto filed with the Commission for the purpose of updating such description.

All documents subsequently filed by the Registrant with the Commission pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) (other than information furnished under Item 2.02 or 7.01 of Form 8-K and exhibits furnished on such form that relate to such items unless such form expressly provides to the contrary) prior to the filing of a post-effective amendment which indicates that all securities offered hereby have been sold or which deregisters all securities then remaining unsold, shall be deemed to be incorporated by reference into this Registration Statement and to be a part hereof from the date of filing such documents.

Any statement contained in a document incorporated or deemed to be incorporated by reference herein shall be deemed to be modified or superseded for purposes of this Registration Statement to the extent that a statement contained in any subsequently filed document that also is deemed to be incorporated by reference herein modifies or supersedes such statement.

Not applicable.

Not applicable.

The Registrant is governed by the Delaware General Corporation Law (“DGCL”). Section 145 of the DGCL provides that a corporation may indemnify any person, including an officer or director, who was or is, or is threatened to be made, a party to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of such corporation), by reason of the fact that such person was or is an officer, director, employee or agent of such corporation or is or was serving at the request of such corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise. The indemnity may include expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with such action, suit or proceeding, provided such officer, director, employee or agent acted in good faith and in a manner such person reasonably believed to be in, or not opposed to, the corporation’s best interest and, for criminal actions or proceedings, had no reasonable cause to believe that such person’s conduct was unlawful. A Delaware corporation may indemnify any person, including an officer or director, who was or is, or is threatened to be made, a party to any threatened, pending or contemplated action or suit by or in the right of such corporation, under the same conditions, except that such indemnification is limited to expenses (including attorneys’ fees) actually and reasonably incurred by such person, and except that no indemnification is permitted without judicial approval if such person is adjudged to be liable to such corporation. Where an officer or director of a corporation is successful, on the merits or otherwise, in the defense of any action, suit or proceeding referred to above, or any claim, issue or matter therein, the corporation must indemnify that person against the expenses (including attorneys’ fees) which such officer or director actually and reasonably incurred in connection therewith.

The Registrant’s Restated Certificate of Incorporation, as amended, (“Charter”), provides for the indemnification of directors to the fullest extent permissible under Delaware law. Accordingly, the Registrant’s directors will not be personally liable for monetary damages for breach of their fiduciary duty as directors, except for liabilities:

The Registrant’s Amended and Restated Bylaws (“Bylaws”) provide for the indemnification of officers and directors acting on the Registrant’s behalf if such persons act in good faith and in a manner reasonably believed to be in or not opposed to the Registrant’s best interest, and, with respect to any criminal proceeding, such indemnified party had no reasonable cause to believe his or her conduct was unlawful.

The Registrant has entered into indemnification agreements with each of the Registrant’s directors and certain of its executive officers. These agreements provide that the Registrant will indemnify each of its directors and certain of its executive officers to the fullest extent permitted by law. The Registrant intends to enter into indemnification agreements with any new directors and executive officers in the future.

The Registrant also maintains a general liability insurance policy which covers certain liabilities of directors and officers of the Registrant arising out of claims based on acts or omissions in their capacities as directors or officers.

The Registrant believes that the limitation of liability provision in the Charter and the indemnification agreements facilitate its ability to continue to attract and retain qualified individuals to serve as directors and officers. The limitation of liability and indemnification provisions in the Charter and Bylaws may discourage stockholders from bringing a lawsuit against directors for breach of their fiduciary duties. They may also reduce the likelihood of derivative litigation against directors and officers, even though an action, if successful, might benefit the Registrant and its stockholders. A stockholder’s investment may be harmed to the extent the Registrant pays the costs of settlement and damage awards against directors and officers pursuant to these indemnification provisions.

Not applicable.

The following documents are filed as exhibits to this Registration Statement:

(a) The undersigned Registrant hereby undertakes:

(1) To file, during any period in which offers or sales are being made, a post-effective amendment to this Registration Statement:

(i) to include any prospectus required by Section 10(a)(3) of the Securities Act;

(ii) to reflect in the prospectus any facts or events arising after the effective date of the Registration Statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the Registration Statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Commission pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than 20% change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective Registration Statement; and

(iii) to include any material information with respect to the plan of distribution not previously disclosed in the Registration Statement or any material change to such information in the Registration Statement;

provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) of this section do not apply if the registration statement is on Form S-8, and the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the Registrant pursuant to Section 13 or Section 15(d) of the Exchange Act that are incorporated by reference in the Registration Statement.

(2) That, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(3) To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

(b) The undersigned Registrant hereby undertakes that, for purposes of determining any liability under the Securities Act, each filing of the Registrant’s annual report pursuant to Section 13(a) or Section 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference in the Registration Statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(c) Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the Registrant pursuant to the foregoing provisions, or otherwise, the Registrant has been advised that in the opinion of the Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in Andover, Commonwealth of Massachusetts, on the 31st day of July, 2023.

POWER OF ATTORNEY

KNOW ALL BY THESE PRESENT, that each individual whose signature appears below hereby constitutes and appoints Edward Durkin as such person’s true and lawful attorney-in-fact and agent with full power of substitution and resubstitution, for such person in such person’s name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this Registration Statement on Form S-8, and to file the same, with all exhibits thereto, and all documents in connection therewith, with the Securities and Exchange Commission granting unto each said attorney-in-fact and agent full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as such person might or could do in person, hereby ratifying and confirming all that any said attorney-in-fact and agent, or any substitute or substitutes of any of them, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed by the following persons in the capacities and on the date indicated.

Exhibit 5.1

July 31, 2023

Casa Systems, Inc.

100 Old River Road

Andover, MA 01810

Re: Securities Being Registered under Registration Statement on Form S-8

We have acted as counsel to you in connection with your filing of a Registration Statement on Form S-8 (the “Registration Statement”) pursuant to the Securities Act of 1933, as amended (the “Securities Act”), on or about the date hereof relating to an aggregate of 2,750,000 shares (the “Shares”) of Common Stock, $0.001 par value per share (“Common Stock”), of Casa Systems, Inc., a Delaware corporation (the “Company”), that may be issued pursuant to a restricted stock unit agreement providing for an employee inducement grant between the Company and an employee, which will be entered into in connection with the commencement of such employee’s employment with the Company pursuant to Nasdaq Listing Rule 5635(c)(4) (the “Inducement Award Agreement”).

We have reviewed such documents and made such examination of law as we have deemed appropriate to give the opinions set forth below. We have relied, without independent verification, on certificates of public officials and, as to matters of fact material to the opinion set forth below, on certificates of officers of the Company.

The opinion set forth below is limited to the Delaware General Corporation Law.

For purposes of the opinion set forth below, we have assumed that no event occurs that causes the number of authorized shares of Common Stock available for issuance by the Company to be less than the number of then unissued Shares.

Based on the foregoing, we are of the opinion that the Shares have been duly authorized and, upon issuance and delivery against payment therefor in accordance with the terms of the Inducement Award Agreement, will be validly issued, fully paid and nonassessable.

This opinion letter and the opinion it contains shall be interpreted in accordance with the Core Opinion Principles as published in 74 Business Lawyer 815 (Summer 2019).

We hereby consent to the inclusion of this opinion as Exhibit 5.1 to the Registration Statement. In giving our consent, we do not admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations thereunder.

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the Registration Statement (Form S-8) pertaining to the Restricted Stock Unit Inducement Award of Casa Systems, Inc. of our reports dated March 15, 2023, with respect to the consolidated financial statements of Casa Systems, Inc. and the effectiveness of internal control over financial reporting of Casa Systems, Inc. included in its Annual Report (Form 10-K) for the year ended December 31, 2022, filed with the Securities and Exchange Commission.

/s/ Ernst & Young LLP

Boston, Massachusetts

July 31, 2023

Exhibit 99.1

CASA SYSTEMS, INC.

Restricted Stock Unit Agreement

Inducement Grant

NOTICE OF GRANT

This Restricted Stock Unit Agreement (this “Agreement”) is made as of the Agreement Date between Casa Systems, Inc. (the “Company”), a Delaware corporation, and the individual named on the signature page hereto (the “Grantee”).

This Agreement includes this Notice of Grant and the following Exhibit A (General Terms and Conditions), which is expressly incorporated by reference in its entirety herein:

IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the Agreement Date. By executing this Notice of Grant, the Grantee hereby acknowledges that the Grantee has read this Notice of Grant and the terms and conditions in the following Exhibit, has received and read the Plan, accepts the Restricted Stock Units subject to all of the terms and provisions of this Agreement (including the applicable provisions of the Plan), and understands and agrees to comply with the terms and conditions of this Agreement (and the Plan insofar as it applies to this Agreement).

Restricted Stock Unit Agreement

Inducement Grant

EXHIBIT A

GENERAL TERMS AND CONDITIONS

For valuable consideration, receipt of which is acknowledged, the parties hereto agree as follows:

1. Inducement Award of Restricted Stock Units.

In consideration of services rendered and to be rendered to the Company by the Grantee, and as an inducement to the Grantee’s acceptance of the Company’s offer of employment, the Company has granted to the Grantee, subject to the terms and conditions set forth in this Agreement, an award (the “Award”) with respect to the number of restricted shares units (the “RSUs”) set forth in the Notice of Grant that forms part of this Agreement (the “Notice of Grant”). Each RSU represents the right to receive one share of common stock, $0.001 par value per share, of the Company (the “Common Stock”) upon vesting of the RSU, subject to the terms and conditions set forth herein. This Award is not issued under the Company’s 2017 Stock Incentive Plan (the “Plan”) and does not reduce the share reserve under the Plan. However, for purposes of interpreting the applicable provisions of this Award, the terms and conditions of the Plan (other than those applicable to the share reserve) shall govern and apply to this Award as if this Award had actually been issued under the Plan. This Award has been granted as an inducement pursuant to Rule 5635(c)(4) of the Marketplace Rules of The NASDAQ Stock Market LLC, and consequently is intended to be exempt from the NASDAQ rules regarding stockholder approval of equity compensation plans. Capitalized terms used but not defined herein will have the same meaning as defined in the Plan. A copy of the Plan has been provided to the Grantee along with this Agreement.

2. Vesting.

(a) The RSUs shall vest in accordance with the Vesting Table set forth in the Notice of Grant (the “Vesting Table”). Any fractional shares resulting from the application of the percentages in the Vesting Table shall be rounded down to the nearest whole number of RSUs.

(b) Upon the vesting of the RSU, the Company will deliver to the Grantee, for each RSU that becomes vested, one share of Common Stock, subject to the payment of any taxes pursuant to Section 7. The Common Stock will be delivered to the Grantee as soon as practicable following each vesting date, but in any event within 30 days of such date. Notwithstanding anything herein to the contrary, in the sole discretion of the Board, the Company may, with respect to any applicable vesting date of the RSU, deliver to the Grantee cash having a fair market value equal to the number of shares of Common Stock underlying the portion of the RSU that vested on such date, payable within 30 days of the vesting date, less applicable taxes.

3. Forfeiture of Unvested RSUs Upon Cessation of Service.

In the event that the Grantee ceases to perform services to the Company for any reason or no reason, with or without cause, all of the RSUs that are unvested as of the time of such cessation shall be forfeited immediately and automatically to the Company, without the payment of any consideration to the Grantee, effective as of such cessation. The Grantee shall have no further rights with respect to the unvested RSUs or any Common Stock that may have been issuable with respect thereto. If the Grantee provides services to a subsidiary of the Company, any references in this Agreement to provision of services to the Company shall instead be deemed to refer to service with such subsidiary.

4. Restrictions on Transfer.

The Grantee shall not sell, assign, transfer, pledge, hypothecate or otherwise dispose of, by operation of law or otherwise (collectively “transfer”) any RSUs, or any interest therein. The Company shall not be required to treat as the owner of any RSUs or issue any Common Stock to any transferee to whom such RSUs have been transferred in violation of any of the provisions of this Agreement.

5. Rights as a Shareholder.

The Grantee shall have no rights as a stockholder of the Company with respect to any shares of Common Stock that may be issuable with respect to the RSUs until the issuance of the shares of Common Stock to the Grantee following the vesting of the RSUs.

6. Provisions of the Plan.

As set forth above, this Award is not granted pursuant to the Plan. However, for the purposes of interpreting the provisions of this Award, of the terms and conditions of the Plan (other than those applicable to the share reserves) shall govern and apply to this Award as if this Award had actually been issued under the Plan.

7. Tax Matters.

(a) Acknowledgments; No Section 83(b) Election. The Grantee acknowledges that he or she is responsible for obtaining the advice of the Grantee’s own tax advisors with respect to the award of RSUs and the Grantee is relying solely on such advisors and not on any statements or representations of the Company or any of its agents with respect to the tax consequences relating to the RSUs. The Grantee understands that the Grantee (and not the Company) shall be responsible for the Grantee’s tax liability that may arise in connection with the acquisition, vesting and/or disposition of the RSUs. The Grantee acknowledges that no election under Section 83(b) of the Internal Revenue Code, as amended, is available with respect to RSUs.

(b) Withholding. The Grantee acknowledges and agrees that the Company has the right to deduct from payments of any kind otherwise due to the Grantee any federal, state, local or other taxes of any kind required by law to be withheld with respect to the vesting of the RSUs. On each vesting date (or other date or time at which the Company is required to withhold taxes associated with the RSUs), the Company will retain from the shares of Common Stock otherwise

issuable on such date a number of shares having a fair market value (as determined by the Company in its sole discretion) equal to the Company’s minimum statutory withholding obligation. If the Company is unable to retain sufficient shares of Common Stock to satisfy such tax withholding obligations, the Grantee acknowledges and agrees that the Company or an affiliate of the Company has the right to deduct from payments of any kind otherwise due to the Grantee any federal, state, local or other taxes of any kind required by law to be withheld for taxes relating to the RSUs. The Company shall not deliver any shares of Common Stock to the Grantee until it is satisfied that all required withholdings have been made and if such withholding taxes cannot be timely satisfied, then the Grantee shall forfeit the RSUs and have no further rights with respect to the award.

8. Miscellaneous.

(a) Authority of Board. In making any decisions or taking any actions with respect to the matters covered by this Agreement, the Board of Directors of the Company (the “Board”) shall have all of the authority and discretion, and shall be subject to all of the protections, provided for in the Plan. Consistent with the terms of the Plan, the Board may delegate any or all of its powers with respect to the matters covered by this Agreement to one or more committees or subcommittees of the Board. All references herein to the Board shall mean the Board or any such committee or subcommittee. All decisions and actions by the Board with respect to this Agreement shall be made in the Board’s discretion and shall be final and binding on the Grantee.

(b) No Right to Continued Service. The Grantee acknowledges and agrees that, notwithstanding the fact that the vesting of the RSUs is contingent upon his or her continued service to the Company, this Agreement does not constitute an express or implied promise of continued service relationship with the Grantee or confer upon the Grantee any rights with respect to a continued service relationship with the Company.

(c) Section 409A. The RSUs awarded pursuant to this Agreement are intended to be exempt from or comply with the requirements of Section 409A of the Internal Revenue Code and the Treasury Regulations issued thereunder (“Section 409A”). The delivery of shares of Common Stock on the vesting of the RSUs may not be accelerated or deferred unless permitted or required by Section 409A.

(d) Grantee’s Acknowledgements. The Grantee acknowledges that he or she: (i) has read this Agreement; (ii) has been represented in the preparation, negotiation and execution of this Agreement by legal counsel of the Grantee’s own choice or has voluntarily declined to seek such counsel; (iii) understands the terms and consequences of this Agreement; and (iv) is fully aware of the legal and binding effect of this Agreement.

(e) Governing Law. This Agreement shall be construed, interpreted and enforced in accordance with the internal laws of the State of Delaware without regard to any applicable conflicts of laws provisions.

Exhibit 107

Calculation of Filing Fee Tables

From S-8

(Form Type)

Casa Systems, Inc.

(Exact Name of Registrant as Specified in its Charter)