February 28, 2015 - UK-based investigative outlet, the Sarawak Report, edited by English journalist Clare Rewcastle Brown, publishes a detailed report accusing Malaysian billionaire Low Taek Jho of siphoning as much as $700 million from 1MDB. The report accuses Low of using PetroSaudi International, an oil company from the Middle East that signed a joint venture deal with 1MDB, as a front to siphon the money.
March 7 - The AFP reports on a letter it received from London-based law firm Schillings, which represented Low, in which he denies the allegations put forward by the Sarawak Report.
March 25 - A special task force is announced to look into 1MDB and its 42 billion ringgit ($11.5 billion) debt. Reports say the task force comprises the Inspector-General of Police (IGP), the Malaysian Anti-Corruption Commission, the Attorney General's Chambers, and the police force.
May 19 - The Malaysian Parliament's Public Accounts Committee (PAC) begins an investigation into 1MDB, according to reports.
June 3 - The Malaysian central bank launches a formal inquiry into 1MDB, requesting the fund hand over information so the central bank can determine if it has violated any of the bank's rules. On the same day, Reuters reports that the fund has released a detailed breakdown of its 42 billion ringgit debt, in order to counter allegations that some of the money is missing.
July 2 - The WSJ publishes a lengthy report on a government probe into the allegations surrounding 1MDB, alleging the probe has traced nearly $700 million flowing from the fund to Najib's personal bank accounts. The PM's office denies the allegations.
July 8 - A Malaysian task force, led by the then-Attorney General Abdul Gani Patail, the country's central bank and the Malaysian Anti-Corruption Commission, which was already investigating the 1MDB developments, freezes bank accounts related to the scandal. Malaysian police raid the offices of 1MDB.
July 19 - The Malaysian Communications and Multimedia Commission, which regulates Malaysia's internet, blocks access to the Sarawak Report from within the country.
July 22 - Singapore police suspend two local bank accounts connected to 1MDB. The Monetary Authority of Singapore says later that it is looking at the bank accounts to ensure they followed proper procedure for financial transactions.
July 27 - Malaysia's Home Ministry suspends the publishing permits of The Edge Weekly and The Edge Financial Daily - both of which belong to the Edge Media Group - for three months as punishment for their reporting on 1MDB. The Edge Financial Daily previously reported about the ongoing 1MDB scandal, including a detailed report claiming Low Taek Jho and PetroSaudi cheated Malaysia of $1.8 billion in cash.
July 28 - Najib carries out a cabinet reshuffle, dropping several ministers including Deputy PM Muhyiddin Yassin and Rural and Regional Development Minister Shafie Apdal. Yassin and Apdal had been critical of Najib's role in 1MDB. Malaysian state news agency, Bermana, reports that Attorney General Abdul Gani Patail was also replaced citing health reasons ahead of his retirement in October.
August 3 - The Malaysian Anti-Corruption Commission finds that 2.6 billion ringgit ($700 million) in Najib's personal account came from donors, not 1MDB, Reuters reports.
August 4 - Malaysian police issue arrest warrant for Clare Rewcastle Brown, editor of the Sarawak Report, on grounds of disseminating false reports on Najib.
August 14 - The ringgit, which had been on a downward trend, plunges to a 17-year low, losing as much as 2.6 percent to 4.1180 per dollar, in part due to concerns about the Federal Reserve's expected rate hike, and also because outside investors are concerned about the turmoil surrounding Najib.
August 21 - Local media report that a new Malaysian task force is being formed to continue the 1MDB investigations, notably leaving out the Malaysian Anti-Corruption Commission. Also, Switzerland's Office of the Attorney General opens criminal proceedings against two financial entities of 1MDB and against an unknown person, according to Reuters. Swiss financial regulator, FINMA, announces that is looking into specific Swiss banks, including whether they did business with 1MDB.
August 25 – The Malaysian Attorney General's office says the new task force is not involved in investigating 1MDB and related companies, but will investigate crimes such as tax evasion and illegal fund flows. Reuters reports that the AG's office says the new task force will, in fact, include staff from the Malaysian Anti-Corruption Commission.
August 29 - An estimated 25,000 people attend a weekend-long anti-government protest calling for the resignation of Najib. Former Malaysian leader Mahathir Mohamad, once a Najib ally, attends the rally.
September 7 - Local media reports the resignation of 1MDB advisory board member Abdul Samad Alias. Samad's resignation came after his repeated requests for a briefing on 1MDB's profits and losses went unanswered by the fund, according to reports.
September 9 – The WSJ reports that officials from an Abu Dhabi-based state investment fund, International Petroleum Investment Co. (IPIC), claim IPIC never received nearly $1.4 billion in payments owed by 1MDB for the purchase of power plants in 2012. 1MDB denies there are payments outstanding from its purchase of power plants in 2012. Draft reports, which the WSJ reviewed showed the $1.4 billion was paid by 1MDB to a IPIC subsidiary, Aabar Investments PJS.
September 10 - Hong Kong police begin a probe into deposits of more than $250 million, allegedly made to accounts related to 1MDB at a Credit Suisse branch in the city, the Financial Times reports. The investigation was prompted by a report to the authorities by vocal critic of 1MDB, Khairuddin Abu Hassan of UMNO. UMNO is also PM Najib's party.
September 14 - The Sunday Times reports the UK Serious Fraud Office is looking into evidence surrounding allegations of possible money laundering and financial fraud, brought against 1MDB by the UK-based Sarawak Report.
Read MoreMalaysia's Leader, Najib Razak, Faces U.S. Corruption Inquiry
September 15 - Swiss investigators are reported to have questioned key witnesses in the 1MDB scandal.
September 16 – As many as 30,000 Malaysians, the majority of whom are from the Malay community, march through Kuala Lumpur in a show of support for the government. Protestors clashed with riot police as they tried to break through barricades in the Chinatown neighborhood, sparking fears of escalating ethnic tension.
September 20 – The WSJ reports that the US Federal Bureau of Investigation (FBI) is the latest of a host of international bodies look into 1MDB. The story cites an unnamed source and says the scope of the FBI investigation is not immediately clear.
September 21 – Local media reports the Malaysian High Court has lifted the three-month suspension of The Edge Financial Daily and The Edge Financial Weekly. Also, the NYT reports that the U.S. Department of Justice is looking into properties held in the U.S. by Najib's stepson and other family friends. The NYT reports investigators are looking into a $681 million payment made to an account believed to be Najib's.
*Conversion based on the ringgit-dollar exchange rate on September 21