CFTA Article 513: Limited Tendering
1. Subject to paragraphs 2 and 3, and provided that it does not use this provision for the purpose of avoiding competition among suppliers or in a manner that discriminates against suppliers of any other Party or protects its own suppliers, a procuring entity may use limited tendering in the following circumstances:
(...)
(c) for additional deliveries by the original supplier of goods or services that were not included in the initial procurement if a change of supplier for such additional goods or services:
(i) cannot be made for economic or technical reasons such as requirements of interchangeability or interoperability with existing equipment, software, services, or installations procured under the initial procurement; and
(ii) would cause significant inconvenience or substantial duplication of costs for the procuring entity;

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CETA Article 19.12.(c) for additional deliveries by the original supplier of goods or services that were not included in the initial procurement if a change of supplier for such additional goods or services:
cannot be made for economic or technical reasons such as requirements of interchangeability or interoperability with existing equipment, software, services or installations procured under the initial procurement; and
would cause significant inconvenience or substantial duplication of costs for the procuring entity.