Open tender is a bidding to be exercised by all willing legal entities and individuals (private business entities) to receive an order for the supply of materials / goods / works / services. If the subject of the competition has a specific and highly specialized character, an open tender with limited participation is conducted. In this tender, companies are prequalified.

Closed tender is a bidding, participation in which can be accepted only for those participants, who were invited by the organizer. The tender is determined to run as closed only in exceptional cases and by decision of the Tender Committee. The right to participate is granted only to those organizations that have sufficient capacity to carry out the entire scope of work, services or supplies of materials / goods needed. 

Reverse auction is a trading with the aim to decrease the prices (Dutch auction). Reverse auction is carried out electronically on online trading platforms. The procedure for carrying out the reverse auction is almost the same as the auction with the aim to lower the price.

When carrying out specialized purchases or solving complex technical issues, the tender is conducted in two stages.