Exhibit 10.3

March 6^th, 2026

Service Agreement

For Engineering and Managerial Consulting Services

between

Oelion AB

as Developer

and

Nuvve Holding Corp.

as Service Provider

and

OMNIA Group Holdings AG

as Guarantor

Contents

THIS SERVICE AGREEMENT FOR ENGINEERING AND MANAGERIAL CONSULTING SERVICE (the “Agreement”) is entered into as of March 6^th, 2026 (“Effective Date”)

BETWEEN

– hereinafter referred to as “Developer” –

– hereinafter referred to as “Service Provider” –

– The companies listed in no. (1) to (2) above are also referred to collectively as the “Parties” and each as the “Party” –

– hereinafter referred to as “Guarantor” –

Preamble

NOW IT IS AGREED as follows:

SERVICE AGREEMENT
FOR ENGINEERING AND MANAGERIAL CONSULTING SERVICE

In this Agreement the following terms and abbreviations shall have the following meanings unless otherwise expressly stated in the individual case:

The Parties and the Guarantor shall comply with all applicable laws, regulations, and regulatory requirements, particularly all relevant Swedish and European Union regulations, including Regulation (EU) 2023/1542 on batteries and waste batteries (EU Battery Regulation), as well as the applicable energy and electricity market regulations.

Confidential Information does not include any Information,

The Developer nor the Guarantor shall be entitled to assign any rights or claims under this Agreement without the written consent of the Service Provider.

The Service Provider shall be entitled to assign or transfer this Agreement, including any and all rights and obligations, receivables, and claims arising hereunder, in whole or in part and without the prior written consent of the Developer or the Guarantor, provided that such assignment or transfer is made to another entity within the Nuvve group.

Unless otherwise provided for in this Agreement, all costs, including fees and expenses, incurred by one Party or the Guarantor in connection with the preparation, negotiation, signing and execution of this Agreement and the transactions contemplated herein, including the costs of advisors, shall be borne by each Party and the Guarantor itself.

All notices and other communications under this Agreement, except as explicitly provided otherwise, shall be made in writing and shall be delivered or sent by registered mail, courier or fax or e-mail with hand-signed PDF attachment to the addresses below or to such other addresses which may be specified by any Party or the Guarantor to the other Party or the Guarantor in the future in writing:

If to the Service Provider:

and with a copy for information purposes only to:

If to the Developer:

If to the Guarantor:

When collecting, processing or using any personal data in the course of certain Services, the Parties and the Guarantor shall comply with all the applicable data protection provisions. To the extent a Party or the Guarantor processes data of the other Party or the Guarantor that is protected by the General Data Protection Regulation (Regulation (EU) 679/2016 (“GDPR”), the Parties and the Guarantor agree to conclude a data processing agreement and/or joint controllership agreement to ensure compliance with the GDPR.

SIGNATURES

Exhibit 3.3(c) – Payment Schedule for Engineering And Managerial Consulting Services

See attachment

Exhibit 6.2.6(a)

Consideration, Milestones and Lock-Up/Leak-Out Agreement

This Exhibit 6.2.6(a) (the “Exhibit”) forms an integral part of the cooperation agreement (the “Cooperation Agreement”) between and among Nuvve Holding Corp. ( “Nuvve”), Oelion AB, a company organized under the laws of Sweden (“Oelion”), and OMNIA Group Holdings AG, a company organized under the laws of Switzerland (“OMNIA” and together with Oelion and Nuvve, the “Parties”). All capitalized terms used but not defined herein shall have the meaning ascribed to them in the Cooperation Agreement. In the event of any inconsistency between this Exhibit and the Cooperation Agreement, the more specific provisions of this Exhibit shall prevail with respect to the consideration, vesting, issuance and Lock-up/Leak-out Agreement (as defined below) described herein.

No issuance, vesting, conversion, or release of any shares of Common Stock (as defined below) or shares of Preferred Stock (as defined below) may occur unless all applicable requirements under U.S. corporate law and Nasdaq rules have been satisfied

The Total Consideration (as defined below) that Nuvve shall provide to the OMNIA Parties shall consist solely of (i) shares of Nuvve’s common stock, par value $0.0001 per share, (the “Common Stock”) and (ii) shares of Series B Convertible Preferred Stock of Nuvve (the “Preferred Stock”).

Prior to the issuance of any consideration to be provided as part of this Exhibit, the Parties shall enter into the lock-up/leak-out agreement substantively in the form listed as Schedule A. All shares of Common Stock and Preferred Stock that make up the Total Consideration pursuant to this Exhibit and the Cooperation Agreement will be subject to that certain lock-up/leak-out Agreement between and among the Parties.

Upon (i) the commencement of operations at the site of the Envisaged Project and (ii) when revenue is first obtained from the site of the Envisaged Project, Nuvve shall issue 814,532 shares of Nuvve’s Common Stock, which is equivalent to 19.9% of Nuvve’s outstanding Common Stock as of the date of execution of the Cooperation Agreement, (the “First Milestone Consideration”) to OMNIA and the SPV shareholders represented by OMNIA (the “OMNIA Parties”).

Upon (i) the approval of Nuvve’s shareholders for the issuance of the shares of Preferred Stock which shall make up the Second Milestone Consideration (as defined below) and (ii) receipt of the initial payment for consulting services as defined in the Service Agreement, Nuvve shall issue shares of Preferred Stock to the OMNIA Parties with the face value of USD$ 15,000,000 (the “Second Milestone Consideration”) minus the value of the First Milestone Consideration.

Upon (i) the approval of Nuvve’s shareholders for the issuance of the shares of Preferred Stock which shall make up the Third Milestone Consideration (as defined below) and (ii) valid transfer of the combined Leasing Agreement and Interconnection Agreement for 50MW from Oelion to Nuvve, Nuvve shall issue shares of Preferred Stock to the OMNIA Parties with a face value of USD$ 5,000,000 (“Third Milestone Consideration”).

Upon (i) the approval of Nuvve’s shareholders for the issuance of the shares of Preferred Stock which shall make up the Fourth Milestone Consideration (as defined below) and (ii) execution of a battery purchase order by Oelion, Nuvve shall issue shares of Preferred Stock to the OMNIA Parties with a face value of USD$ 20,000,000 (the “Fourth Milestone Consideration”“).

Upon (i) the approval of Nuvve’s shareholders for the issuance of the shares of Preferred Stock which shall make up the Fifth Milestone Consideration (as defined below) and (ii) delivery and delivery verification of the 50MW/75MWh battery, Nuvve shall issue shares of Preferred Stock to the OMNIA Parties with a face value of USD$ 25,000,000 (the “Fifth Milestone Consideration”)).

Upon (i) the approval of Nuvve’s shareholders for the issuance of the shares of Preferred Stock which shall make up the Sixth Milestone Consideration (as defined below) and (ii) formal installation approval from the Swedish government and (iii) confirmation of platform control from Nuvve’s system, Nuvve shall issue shares of Preferred Stock to the OMNIA Parties with a face value of USD$ 25,000,000 (the “Sixth Milestone Consideration”)

Upon (i) the approval of Nuvve’s shareholders for the issuance of the shares of Preferred Stock which shall make up the Seventh Milestone Consideration (as defined below) and (ii) formal bid participation in the applicable market and (iii) approval of the bid, Nuvve shall issue shares of Preferred Stock to the OMNIA Parties with a face value of USD$ 30,000,000 (the “Sixth Milestone Consideration” and together with the First Milestone Consideration, the Second Milestone Consideration, the Third Milestone Consideration, the Fourth Milestone Consideration, the Fifth Milestone Consideration, the Sixth Milestone Consideration, and the Seventh Milestone Consideration, the “Total Consideration”).

Schedule A

Lock-up/Leak-out Agreement

LOCK-UP LEAK-OUT AGREEMENT

This LOCK-UP LEAK-OUT AGREEMENT (this “Agreement”) is made and entered into as of [__], 2026, by and between Nuvve Holding Corp., a Delaware corporation (the “Company”) on one hand, and OMNIA Group Holdings AG, a company organized under the laws of Switzerland and Oelion AB, a company organized under the laws of Sweden on the other hand (collectively, the “Stockholder”). For purposes of this Agreement, “Stockholder” includes any affiliate or controlling person of Stockholder, and any other agent, representative or other person with whom Stockholder is acting in concert.

WHEREAS, the Company and the Stockholder are party to that certain Cooperation Agreement, dated March 6, 2026, and pursuant to such agreement, the Stockholder is entitled to receive shares of the Company’s common stock, par value $0.0001 per share (“Common Stock”) and shares of the Company’s Series B Convertible Preferred Stock (“Series B Convertible Preferred Stock”).

WHEREAS, the Stockholder has agreed to enter into this Agreement, which shall restrict the public sale, assignment, transfer, conveyance, hypothecation, or alienation of all shares of the Common Stock and Series B Convertible Preferred Stock, whether now beneficially owned or hereafter acquired (by any means whatsoever) by the Stockholder (the foregoing shares, collectively, the “Shares”).

NOW, THEREFORE, in consideration of the foregoing premises and of the mutual covenants contained herein, the receipt and sufficiency of which are hereby acknowledged, the parties hereby agree as follows:

AGREEMENT

1. The Stockholder acknowledges that as of the date hereof, (a) the Shares have not been registered under the Securities Act of 1933, as amended (the “Securities Act”) and are considered “restricted securities,” and (b) the Shares may only be sold, transferred, hypothecated or otherwise disposed of by the Stockholder in accordance with Rule 144 promulgated under the Securities Act.

2. Except as otherwise expressly provided herein, commencing on the execution and delivery of this Agreement and ending on the thirtieth (30^th) day following the date that each such shares of Common Stock or shares of Preferred Stock are first issued, as applicable (such period, the “Lock-Up Period”), the Stockholder, including its affiliates, may not offer, pledge, gift, donate, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right, or warrant to purchase, lend, or otherwise transfer or dispose of, directly or indirectly, any of the Shares, or enter into any swap, option (including, without limitation, put or call options), short sale, future, forward, or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of the Shares, whether any such transaction is to be settled by delivery of shares of the Common Stock, Preferred Stock or such other securities, in cash or otherwise.

2.1 All Shares subject to this Agreement will, at the Company’s option, bear an applicable legend referencing this Agreement and will be subject to irrevocable instructions delivered to the transfer agent concurrently herewith in form and substance satisfactory to the Stockholder to ensure prompt compliance with the terms of this Agreement, including providing for releases of the Shares or removal of legends as set forth in such instructions. Such instructions will include a direction requiring the transfer agent to deliver to each party to this Agreement upon request a report setting forth the holdings of the Stockholder and any transfers that may have occurred.

2.2 The Stockholder agrees that it will not, directly or indirectly, engage in any short selling, hypothecation of the Shares or by any other manner or method sell or lend Shares that would be adverse to the publicly traded shares of the Company during the Lock-Up Period or Leak-Out Period (as defined below).

2.3 Any permitted transferee of any of the Shares covered by this Agreement, other than purchasers in transactions permitted under a waiver by the Company pursuant to Section 3, shall be subject to all of the terms and conditions of this Agreement, including, without limitation, all restrictions on the resale of such Shares, and for all such purposes, any such transferee shall be a “Stockholder” as defined herein.

2.4 Any purported transfer of Shares in violation of this Agreement shall be void and of no force or effect, and no such transfer shall be made or recorded on the books of the Company.

2.5 Subject to the terms of this Agreement, the Stockholder agrees that for a period beginning immediately upon the end of the Lock-Up Period and ending twelve (12) months from such date (the “Leak-Out Period”), the Stockholder shall have the right to sell, on any trading day, up to twenty percent (20%) of the total trading volume of the Company’s common stock for the current trading day.

3. Notwithstanding anything to the contrary set forth herein, the Company may, in its sole discretion and in good faith, at any time and from time to time, waive any of the conditions or restrictions contained herein.

4. In the event of: (a) a completed tender offer to purchase all or substantially all of the Company’s issued and outstanding securities; or (b) a merger, consolidation or other reorganization of the Company with or into an unaffiliated entity, then this Agreement shall terminate as of the closing of such transaction and the Shares restricted pursuant hereby shall be released from such restrictions.

5. Except as otherwise provided in this Agreement or any other agreements between the parties hereto, the Stockholder shall be entitled to its respective beneficial rights of ownership of the Shares, including, if applicable, the right to vote the Shares, if then issued, for any and all purposes.

6. All notices and other communications hereunder shall be in writing and shall be acceptable if (a) delivered personally, by facsimile, or by e-mail, so long as the parties to this Agreement receive such notices at the addresses set forth below the parties’ signatures to this Agreement (with confirmation of receipt), (b) if sent by registered or certified mail (return receipt requested) and postage prepaid, or (c) if sent by reputable overnight courier, so long as the parties to this Agreement receive such notices at the addresses set forth below the parties’ signatures to this Agreement or at such other address for a party as shall be specified by like notice. All notices shall be deemed to be given on the same day if delivered by hand, facsimile, or by e-mail or on the following business day if sent by overnight delivery or the second business day following the date of mailing.

7. The resale restrictions on the Shares set forth in this Agreement shall be in addition to all other restrictions on transfer imposed by applicable United States and state securities laws, rules, and regulations.

8. If the Company or the Stockholder fails to fully adhere to the terms and conditions of this Agreement, such party shall be liable to the other party hereto for any damages suffered by any party hereto by reason of any such breach of the terms and conditions hereof. The Stockholder agrees that in the event of a breach of any of the terms and conditions of this Agreement by the Stockholder, that in addition to all other remedies that may be available in law or in equity to the non-defaulting parties, the Company may seek a preliminary and permanent injunction, without bond or surety, and an order of a court requiring the Stockholder to cease and desist from violating the terms and conditions of this Agreement and specifically requiring the Stockholder to perform his/her/its obligations hereunder is fair and reasonable by reason of the inability of the parties to this Agreement to presently determine the type, extent or amount of damages that the Company or its other stockholders may suffer as a result of any breach or continuation thereof. Nothing herein contained shall be construed as prohibiting the Company from pursuing any other remedies available to it for such breach or threatened breach, including, without limitation, issuing stop transfer instructions to the Company’s transfer agent in connection with any purported transfer of the Shares in violation of the provisions of this Agreement.

9. This Agreement sets forth the entire understanding of the parties hereto with respect to the subject matter hereof and may not be amended except by a written instrument executed by the parties hereto.

10. This Agreement shall be governed by and construed in accordance with the laws of the State of Delaware. In the event of default hereunder, the non-defaulting party shall be entitled to recover reasonable attorneys’ fees incurred in the enforcement of this Agreement.

11. The Stockholder represents that before executing this Agreement he/she/it had the opportunity to consult with competent legal counsel of his/her/its own choosing, carefully read the Agreement, and has been fully and fairly advised as to its terms. The parties hereto agree that any rule of law or decision that would require interpretation of any claimed ambiguities in this Agreement against the party that drafted it has no application and is expressly waived.

12. This Agreement may be executed in multiple counterparts, each of which shall be deemed an original for all purposes and all of which shall be deemed, collectively, one agreement. The parties hereto, and their respective successors and assigns, are hereby authorized to rely upon the signature of each person on this Agreement, which are delivered by facsimile, electronic signature or scanned electronic e-mail attachment, as constituting a duly authorized, irrevocable, actual, current delivery of this Agreement with original ink signatures of each such person. Signatures of the parties transmitted by facsimile or scanned e-mail attachment shall be deemed to be their original signatures for all purposes. This Agreement shall become effective when executed and delivered by the parties hereto.

13. In case any one or more of the provision contained in this Agreement is for any reason held to be invalid, illegal, or unenforceable in any respect, such invalidity, illegality, or unenforceability shall not affect any other provision of this Agreement, and such invalid, illegal, or unenforceable provision shall be reformed and construed so that it will be valid, legal, and enforceable to the maximum extent permitted by law.

[Remainder of Page Left Intentionally Blank; Signature Page Follows]

IN WITNESS WHEREOF, the undersigned have duly executed and delivered this Lock-Up Leak-Out Agreement as of the day and year first above written.