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THIS ANNOUNCEMENT CONTAINS INSIDE INFORMATION

FOR IMMEDIATE RELEASE

London, 14 May 2026

Further update regarding Kazakhstan withholding tax disputes

Nostrum Oil & Gas PLC (LSE: NOG) (the "Company" and together with its subsidiaries, the "Group"), an independent oil and gas company engaging in the production, development and exploration of oil and gas in the pre-Caspian Basin of Western Kazakhstan, provides a further update on withholding tax disputes involving its principal operating subsidiary, Zhaikmunai LLP ("ZKM") and the tax authorities in the Republic of Kazakhstan ("RoK"), following on from its announcements on 3 February 2026, 9 February 2026 and 17 February 2026.

On 13 May 2026, the first instance court of the RoK informed ZKM that it had rejected ZKM's challenge to tax claims by the RoK tax authorities resulting from their tax audits of ZKM for the years 2018 and 2019.

As previously announced, the Company believes that the tax claims made by the RoK tax authorities resulting from their tax audits of ZKM for the years 2018, 2019 and 2020, which deny ZKM the benefit of relevant and valid exemptions from, or reductions to, withholding tax payable under RoK law on certain bonds issued by Group companies, remuneration on an intra-Group loan, and income from consulting services, respectively, are without merit.

Whilst the Company has not yet received the court's written judgment, the Company is extremely disappointed with the decision of the first instance court, as it believes the decision is not consistent with applicable laws. ZKM intends to appeal the first instance decision. The Company is also considering its international treaty-based remedies and will continue to defend its interests.

The Company continues to monitor developments closely and further updates will be issued as appropriate.

LEI: 2138007VWEP4MM3J8B29

Further information

For further information please visit www.nostrumoilandgas.com

Further enquiries

Nostrum Oil & Gas PLC                                                

Yelena Zhuravleva, CFO

[email protected]                                                                                                     

TEAM LEWIS                                                                                         

Galyna Kulachek

+ 44 (0) 20 7802 2664

[email protected]

About Nostrum Oil & Gas

Nostrum Oil & Gas PLC is an independent energy company with gas processing infrastructure and an export hub in north-west Kazakhstan. Its shares are listed on the London Stock Exchange (ticker symbol: NOG). The principal producing asset of Nostrum Oil & Gas PLC is the Chinarevskoye field which is operated by its wholly-owned subsidiary Zhaikmunai LLP, which is the sole holder of the subsoil use rights with respect to the development of the Chinarevskoye field. The Company also owns an 80% interest in Positiv Invest LLP, which holds the subsoil use rights for the "Kamenskoe" and "Kamensko-Teplovsko-Tokarevskoe" areas in the West Kazakhstan region (the Stepnoy Leopard fields).

Forward-Looking Statements

Some of the statements in this document are forward-looking. Forward-looking statements include statements regarding the intent, belief and current expectations of the Company or its officers with respect to various matters. When used in this document, the words "expects", "believes", "anticipates", "plans", "may", "will", "should" and similar expressions, and the negatives thereof, are intended to identify forward-looking statements. Such statements are not promises nor guarantees and are subject to risks and uncertainties that could cause actual outcomes to differ materially from those suggested by any such statements.

No part of this announcement constitutes, or shall be taken to constitute, an invitation or inducement to invest in the Company or any other entity, and shareholders of the Company are cautioned not to place undue reliance on the forward-looking statements. Save as required by the relevant listing rules and applicable law, the Company does not undertake to update or change any forward-looking statements to reflect events occurring after the date of this announcement.