6 banks just lost more than $200 million on the Pfizer-Allergan collapse

The Pfizer-Allergan merger - a deal that would have been worth $160 billion - has officially been scrapped and it's bad news for investment banks.

The US Treasury Department on Monday tightened the rules around tax inversions, the type of transaction Pfizer is trying to pull off with Allergan.

Now the deal has been called off and the two companies' advisers could lose a combined $236 million in fees, according to the consulting firm Freeman & Co.

If the deal collapses, the banks may get 10% of that.

Goldman Sachs, Centerview Partners, Guggenheim, and Moelis had been advising Pfizer on the deal, while JPMorgan and Morgan Stanley were working for Allergan.

Another deal - the proposed merger of Halliburton and Baker Hughes - is also at risk of derailing this week. The US Department of Justice (DOJ) is reportedly readying an antitrust lawsuit to block that merger.

The three banks advising on that deal - Bank of America, Credit Suisse, and Goldman Sachs - are due to receive $110 million in fees and could lose the bulk of it if the deal unravels.