1. Tax returns

Treasury Secretary Steven Mnuchin is blocking Congress’s request for Trump’s tax returns, a demand based on a 1924 anti-corruption law. On Friday, House Ways and Means Committee Chairman Richard E. Neal (D-Mass.) subpoenaed Mnuchin and Charles Rettig, the commissioner of the Internal Revenue Service. Democrats say they are ready to take the matter to court if need be.

2. The Mueller report

The White House asserted executive privilege over the full report issued by special counsel Robert S. Mueller III on Wednesday after Democrats tried to subpoena the underlying evidence in their probe of whether Trump obstructed justice. Democrats are preparing to hold Attorney General William P. Barr in contempt of Congress for refusing to honor their subpoena.

According to Congress, the Justice Department should provide it with underlying evidence. Just as long as the investigation’s subject is of the opposite party. (JM Rieger/The Washington Post)

3. McGahn testimony

The White House has told former White House counsel Donald McGahn to ignore a House Judiciary Committee subpoena for documents pertaining to the Mueller investigation. McGahn was a central witness in several of 10 instances of potential obstruction identified by Mueller. He also could face being held in contempt of Congress if he refuses to appear to testify later this month.

4. Mazars

Trump’s personal and Trump Organization attorneys are suing the House Oversight Committee and his accounting firm, Mazars, to quash a subpoena for his financial information. The lawsuit cites an 1880s precedent that has been overturned and dormant for nearly 100 years. A judge recently agreed to fast-track the proceedings and could make a ruling as early as Tuesday.

Lawmakers are split along partisan lines over whether to further investigate possible areas of obstruction of justice by President Trump. (Meg Kelly/The Washington Post)

5. Deutsche Bank and Capital One

Trump’s personal attorneys and Trump Organization lawyers are suing to block his former lender and bank from handing over similar financial documents related to a congressional investigation into Russia money laundering as well as political interference in the 2016 election.

6. Trump-Putin meetings

The Trump administration declined to comply with requests for documents and communications related to Trump and President Vladimir Putin’s private discussions. The Washington Post reported that Trump tried to conceal the contents of one discussion by taking possession of his own interpreter’s notes and instructing a linguist present not to discuss what had transpired.

7. Emoluments

Trump is defending himself in two lawsuits that say his company violates the Constitution by doing business with foreign governments. Justice Department lawyers representing the president have succeeded in temporarily blocking subpoenas by the attorneys general of D.C. and Maryland for financial records and other documents related to Trump’s Washington D.C. hotel. A second lawsuit was filed by 200 congressional Democrats.

The Trump administration has been slow to turn over information regarding the lease for Trump International Hotel in Washington, which rents the historic federally owned Old Post Office Pavilion. Democrats say they have only received what they called a “partial” response for documents as part of the investigation being conducted by the Transportation and Infrastructure and Oversight committees.

9. FBI building

Five House panels have demanded records involving a decision to stop the relocation of the FBI headquarters to the suburbs of Washington. Democrats believe Trump was involved in the decision to prevent the building - located across the street from the Trump International Hotel - from being replaced by a hotel that could compete for business. There has been no response from any of the agencies from which they have asked for information.

10. Hush-money payments

The House Oversight Committee sent letters in January and February demanding more information about payments made by the president’s former personal lawyer, Michael Cohen, to an adult-film actress who said she had an affair with Trump. The White House allowed the committee to review some documents in person, but Democrats are continuing to demand the full records.

11. Security clearances

The White House has refused to answer most of the House Oversight Committee’s questions and document demands related to its security clearance process. Trump leaned on then-Chief of Staff John F. Kelly to grant his son-in-law Jared Kushner a security clearance despite concerns from intelligence officials. Kushner was among more than 20 people whose security clearances were approved despite objections raised by national security officials, according to staffer Tricia Newbold.

12. Family separation policy

The administration has not fully responded to document requests or testimony from multiple committees on a policy that separated migrant children from their parents. The Health and Human Services Department has partially responded to House Energy and Commerce Committee demands for documents and communications related to the policy. Other committees, including Judiciary, Homeland and Oversight panels, say they are still awaiting answers.

13. Other immigration issues

The administration has not answered inquiries about a proposal to bus migrant children to sanctuary cities and the reasons for a leadership shake-up at the Department of Homeland Security. On the latter, the House Homeland Security Committee expects a response before it holds a DHS budget hearing on May 22. The House Oversight Committee is also investigating the issue.

14. National emergency declaration

The White House has ignored Judiciary Committee inquiries into the legal basis of Trump’s emergency declaration aimed at building a wall or fencing on the southern border. Trump declared the state of emergency on the border after a 35-day shutdown failed to result in a deal giving him billions for his proposed wall, which he had repeatedly promised would be paid for by Mexico.

15. Obamacare repeal

The Trump administration has refused to discuss the process by which it decided to challenge the Affordable Care Act in court, sending the committees demanding the information only a confirmation that it had received their letters.

16. Puerto Rico

The House Oversight Committee on Monday revived an investigation into the federal government’s response to Hurricane Maria by sending letters to the White House, Health and Human Services and the Federal Emergency Management Agency. The committee is asking for all documents by May 20. In the fall of 2017, the committee had made a ipartisan request for those records to DHS and FEMA. Democrats say they did not receive answers.

17. Census

Barr has blocked Justice Department official John Gore from appearing for subpoenaed testimony on the addition of a citizenship question on the 2020 Census, an idea that reportedly began in the White House. Democrats have called the question unlawful and say it is aimed at depressing the number of undocumented immigrants tallied in the census.

18. Saudi nuclear transfer

The White House has refused to answer Oversight Committee questions or document requests on a proposal to transfer highly sensitive U.S. nuclear technology to Saudi Arabia.

19. White House use of private email

The Oversight panel has sought more information surrounding allegations that White House officials have conducted work on private email, including Trump’s daughter and adviser, Ivanka Trump. The White House has said it feels it has addressed the matter, but Democrats are pressing for more documents.

20. Kushner Saudi trip

The House Foreign Affairs Committee has asked for documents and information related to a February trip taken by Kushner, Trump’s son-in-law and senior adviser, to Saudi Arabia, where he reportedly met with Crown Prince Mohammed bin Salman. According to the committee, which has asked Secretary of State Mike Pompeo to brief the panel on the purpose of the trip, U.S. Embassy diplomats were left out of the meetings.