Tax dodging, dealmaking and startups: WHAT YOU NEED TO KNOW ON WALL STREET

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It is all about taxes right now on Wall Street.

The Treasury Department on Monday announced tighter rules for tax inversions, sending shares in Allergan, a company which is in the middle of such a deal, plummeting.

US President Barack Obama backed that up on Tuesday, saying inversions hurt ordinary Americans who do not have the financial muscle to take advantage of loopholes in the tax system.

And it turns out that the state of New Jersey has to rethink its budget because billionaire hedge fund manager David Tepper moved.

In other news, the Panama Papers have claimed their first victim: Iceland's Prime Minister has resigned after revelations around his involvement in an offshore company.

The most important part of the US economy just made a comeback, Goldman Sachs is dominating dealmaking, and Valeant finally had some decent news,

A trading startup backed by George Soros and Peter Thiel has undergone a big shake-up, and investors are overlooking Apple's next $50 billion business.

Hedge funds and venture capitalists alike are turning to this new Silicon Valley startup for their next information edge.

And Goldman Sachs just sent out this quiz to clients - see how many questions you can get right.

Here are the top Wall Street headlines at midday:

Alaska Airlines massively overpaid for Virgin America, and it's a deceptively smart move - Seattle-based Alaska Airlines announced Monday that it would acquire Virgin America for $2.6 billion after a short bidding war with JetBlue.

Tesla blames 'hubris' over the Model X as it falls short of quarterly delivery target - Tesla reported on Monday that it had delivered 14,820 vehicles in the first quarter of 2016, short of the 16,000 the company said it would sell.

Here's JP Morgan's complete guide to the markets - After a wild start to 2016, there's a lot to make sense of in markets right now.

TOM LEE: Stocks will hit all-time highs by the summer - Fundstrat's Tom Lee is still super bullish.

EL-ERIAN: Here are 10 things you should be closely watching in the global economy - Roller-coaster views about global growth were important contributors to the first quarter's dramatic "V"-shaped stock market performance