The CNBC Network reported that the deal is confirmed, and Salesforce may officially announce the acquisition of Slack tomorrow, after the market closes. Salesforce is planning to acquire Slack by paying half in cash and half in shares.

Salesforce’s major acquisitions so far:

Tableau – $ 15.3 billion
MuleSoft – $ 6.5 billion
ExactTarget (Salesforce Marketing Cloud) – $ 2.5 billion
Demandware (Salesforce Commerce Cloud) – $ 2.5 billion
ClickSoftware – $ 1.35 billion

Slack could end up being Salesforce’s biggest acquisition. Slack’s current market capitalization is $ 24.57 billion. Therefore, Salesforce can pay around $ 30 billion to acquire Slack.

Slack’s shares were up 4.4% to $ 42.45 on the news, with its previous closing price giving the company a valuation of $ 23.2 billion. Salesforce shares fell 3.7% to $ 238.90 on Monday.