The process of concluding a contract by auction results is regulated by section 36.-37 of the Law of Ukraine "On Public Procurement". Part 4 of Article 36 contains a rule according to which the essential terms and conditions of the contract cannot be changed after its signing to fulfill obligations by the parties in full, except for the following cases:
- reduction of purchases, in particular taking into account the actual amount of procurer's expenses;
- changes in the unit price not more than 10 percent in case of fluctuations in the price of such goods on the market. The specified must not lead to an increase in the amount specified in the contract;
- improvement of the quality of the subject of procurement in case such improvement does not lead to an increase in the amount specified in the contract;
- prolongation of the contract and fulfillment of obligations for the transfer of goods,
- performance of works, provision of services in the case of documented objective circumstances that caused such continuation, including force majeure, delay of financing of procurer's expenses, if such changes will not lead to an increase in the amount specified in the contract;
- a coordinated change of price in the direction of reduction (without changing the quantity (volume) and quality of goods, works and services);
- price changes due to changes in tax rates and fees in proportion to changes in such rates;
- changes in the index of consumer prices established by the legislation of the state statistics bodies, changes in the exchange rate of foreign currencies, changes in stock quotes or Platts indicators, regulated prices (tariffs) and standards applied in the procurement contract, if purchase price order is provided;
- changing the conditions due to the application of the provisions of part five of this article.
Consequently, amendments to the procurement contract concluded on the basis of the results of the negotiation procedure are possible in terms of essential conditions, only if one or more of the above grounds are present.