After a senior Iranian official was killed by drone strike, Congressional members balked at how the White House had failed to brief them on the attack. Trump said via tweet that no notice is required (in direct contradiction with the 1973 War Powers Act), but that his Twitter posts would serve as notice to Congress.

He has similarly failed to brief Congress for strikes, including when he told Russia and Turkey of an impending attack on an ISIS leader before anyone in Congress.

Business Insider – Trump claims his ‘Media Posts’ on Twitter now count as official notification to Congress about any plans to attack Iran
Stars and Stripes – Trump claims his tweets are sufficient notice to Congress that US might strike Iran