SEC Form DEFA14A filed by NioCorp Developments Ltd.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a)

of the Securities Exchange Act of 1934 (Amendment No. ___)

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 under §240.14a-12

NIOCORP DEVELOPMENTS LTD.
(Name of Registrant as Specified in its Charter)

Not Applicable.
(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.

NOTICE-AND-ACCESS NOTIFICATION

Important Notice Regarding the Availability of Proxy Materials for the Annual General
Meeting of Shareholders to Be Held on April 6, 2026

Dear Shareholder:

You are receiving this Notice-and-Access Notification because NioCorp Developments Ltd. (the "Company") has decided to use the notice-and-access model for delivery of meeting materials for its annual general meeting of shareholders to be held on April 6, 2026 (the "Meeting") to its registered shareholders and Canadian and U.S. beneficial shareholders. This Notice-and-Access Notification regarding the Meeting is prepared pursuant to the notice-and-access rules that came into effect on February 11, 2013 under National Instrument 54-101 - Communication with Beneficial Owners of Securities of a Reporting Issuer, National Instrument 51-102 - Continuous Disclosure Obligations and Rule 14a-16 under the United States Securities Exchange Act of 1934, as amended. Under the notice-and-access method of distribution, instead of paper copies of the Notice of Meeting, Management Information and Proxy Circular (the "Information Circular"), 2025 Annual Report and form of proxy (the “Proxy” and, together with the Notice of Meeting, the Information Circular and the 2025 Annual Report, the "Meeting Materials"), shareholders receive this Notice-and-Access Notification with information on how they may access such materials electronically. This communication is not a form for voting and presents only an overview of the more complete information in the Meeting Materials, which contain important information and can be accessed online or requested by mail as provided below. We encourage you to access and review all of the important information contained in the Meeting Materials before voting.

The Company has elected not to use the procedure known as "stratification" in relation to its use of the notice-and-access rules. Stratification occurs when a reporting issuer using the notice-and-access rules provides a paper copy of proxy-related materials to some, but not all, of its shareholders.

MEETING DATE AND LOCATION

Only shareholders who owned common shares of the Company at the close of business on the record date of February 9, 2026, may vote at the Meeting or any adjournment or postponement of the Meeting. The purposes of the Meeting are:

SHAREHOLDERS ARE REMINDED TO ACCESS AND REVIEW THE MEETING MATERIALS PRIOR TO VOTING

The Meeting Materials can be viewed online under the Company’s SEDAR+ profile at www.sedarplus.com or on the Company’s website at https://www.niocorp.com/investor-center/annual-meetings/ for up to one year from the date of this Notice-and-Access Notification.

HOW TO OBTAIN PAPER COPIES OF THE MEETING MATERIALS

You can obtain a paper copy of the Meeting Materials, as well as materials for all future shareholder meetings, free of charge, by providing your name and mailing address to the Company in one of the following manners:

Requests may be made up to one (1) year from the date the Information Circular was filed on SEDAR+, but requests should be received by the Company at least five (5) business days in advance of April 2, 2026, being the proxy cut-off date for voting at the Meeting, in order to receive the Meeting Materials in advance of the proxy cut-off date for the Meeting. If you do not request paper copies of the Meeting Materials, they will not otherwise be provided to you.

If interested, you may attend the Meeting in person. Directions to attend the Meeting where registered shareholders may vote in person can be found on our website at https://www.niocorp.com/investor-center/annual-meetings/.

VOTING

PLEASE NOTE – YOU CANNOT VOTE BY RETURNING THIS NOTICE-AND-ACCESS NOTIFICATION. To vote your securities, you are asked to return your proxy using one of the following methods not later than 10:00 a.m. Mountain Daylight Time, on April 2, 2026, being the proxy cut-off date for the Meeting:

REGISTERED HOLDERS are asked to return their proxy using the following methods by the proxy deposit date noted on your proxy:

ALL NON-REGISTERED HOLDERS should follow the instructions on the materials provided by your broker or such other intermediary.

To vote by telephone or the Internet, you will need to provide your CONTROL NUMBER.

QUESTIONS

Shareholders with questions about notice-and-access can contact the Company at (720) 334-7066, or via email at IR@niocorp.com.