Can traders agree on prices before they submit their tenders?

It is not permissible for the traders to agree on prices
before submitting their tenders, because that harms the one who is seeing
the deal, who only invited them to submit their tenders in order to get the
best deal. The Prophet (peace and blessings of Allaah be upon him)
said: “Leave the people alone (to engage in trade), and Allaah will provide
for some of them by means of others.” Narrated by Muslim, 1522. Moreover,
agreeing in advance and sharing out the deal among the traders without the
knowledge of the agent is deceiving him, and in the hadeeth it says,
“Whoever deceives us is not one of us.” Narrated by Muslim, 101. 

The Standing Committee was asked about buyers at an auction
agreeing not to increase the price beyond a specific limit. They replied: 

The agreement between buyers to stop when the price at an
auction reaches a certain limit is a kind of selfishness, which will cause
harm to the sellers of the product. Both selfishness and harming others are
forbidden. This is a bad attitude that does not befit the Muslims and is not
approved of by Islamic sharee’ah. The seller who is affected by such a
conspiracy not to raise the price beyond a pre-set limit has the choice, if
he realizes that he has been cheated, of either annulling the sale or
allowing it to proceed. 

Fataawa al-Lajnah al-Daa’imah,
13/114. 

The Muslim should strive
to ensure that his food comes from good, halaal sources. The Prophet
(peace and blessings of Allaah be upon him) said: “Every body that is
nourished from haraam sources, the Fire is more suited for it.” Narrated by
al-Tabaraani and Abu Na’eem from Abu Bakr; classed as saheeh by al-Albaani
in Saheeh al-Jaami’, no. 4519.

 It was also narrated by al-Tirmidhi, 614, from the hadeeth
of Ka’b ibn ‘Ajrah, where the wording is: “No flesh grows that was nourished
from haraam sources, but the Fire is more suited for it.” 

May Allaah protect us and you from the evil thereof. 

And Allaah knows best.