I would think so.

In other words Mueller could have them and tRump may not even know?

he's added attorneys to his team that specialize in RICO and money laundering.

But there are no leaks coming from Mueller's team and I don't expect that to change.

Mueller is smart, what they do have is a drop dead plan in place. Meaning that if they get fired by Trump and the investigation closed by the next guy, they probably have a dead man's switch employed. The info they have gathered will not be erased or buried.

By having no leaks, Mueller has protected himself from Trump firing him. If there were leaks it could be used as an excuse to get rid of him. It wouldn't surprise me though that if there are leaks in the near future they are Red Herrings, Mueller could leak that they are exonerating Trump so Trump allows the investigation to continue.

It doesn't take a partisan to see that the Russia story is the most weighty story for our Democracy since the Civil War. It's going to be beyond explosive, it's going to shake the foundation of our country.

I was thinking more of the tRump administration leaking since that's what they like to do. Rats off the ship.

the Obama administration leaving a heavy paper trail when they left in regards to Trump Russia?

https://www.nytimes.com/2017/03/01/us/politics/obama-trump-russia-election-hacking.html?mtrref=www.bing.com&gwh=76980D87F08E9D4EC43F6FB5331A1950&gwt=pay

I would imagine Mueller is doing much of the same.

tax matters, to certain 'Federal officers or employees'. They must submit an application to a judge consistent with the rules (shown below).

In the Justice Department's guidelines in this area, the example format for the application includes a request that the application and order be maintained under seal, so if Mueller has made a request, Trump likely would not know about it. Also, once a special prosecutor, Assistant US Attorney, etc. receives tax return information from the IRS, they are still bound by law as to whom they can reveal the information during the investigation efforts. The DOJ's application requires the names of each person who will need access to the information. So, if Mueller does request/receive the tax returns, his team of star attorneys are not going to commit a felony that could jeopardize the investigation and hurt - if not destroy - their careers by leaking anything about them.

Here's part of the related US Code:

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Section 6103(i): Disclosure to Federal officers or employees for administration of Federal laws not relating to tax administration
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(B) Application for order:

The Attorney General, the Deputy Attorney General, the Associate Attorney General, any Assistant Attorney General, any United States attorney, any special prosecutor appointed under section 593 of title 28, United States Code, or any attorney in charge of a criminal division organized crime strike force established pursuant to section 510 of title 28, United States Code, may authorize an application to a Federal district court judge or magistrate judge for the order referred to in subparagraph (A). Upon such application, such judge or magistrate judge may grant such order if he determines on the basis of the facts submitted by the applicant that—

(i) there is reasonable cause to believe, based upon information believed to be reliable, that a specific criminal act has been committed,
(ii) there is reasonable cause to believe that the return or return information is or may be relevant to a matter relating to the commission of such act, and
(iii) the return or return information is sought exclusively for use in a Federal criminal investigation or proceeding concerning such act (or any criminal investigation or proceeding, in the case of a matter relating to a missing or exploited child), and the information sought to be disclosed cannot reasonably be obtained, under the circumstances, from another source.

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but that shouldn't be difficult, really. However, it wouldn't get leaked, I'm sure, if he has them or gets them. They might eventually be made public, but that's a far more complicated process. They could be subpoenaed by a congressional investigation, I believe, but they'd also have to be kept private.

keeping everything every close to his chest and it is a tribute to the professionals he has hired that there have been no leaks. If the tax returns are as bad as we think they are, Mueller may also be concerned about a constitutional crisis when the information eventually comes out. You know, any of us who lived through Watergate have to admit that as much as we deplored Richard Nixon, he left the Republic intact. I'm not so sure Trump will do the same. We are perilous waters and we have a madman at the helm.