The apex court said that the allocations were made arbitrary and that there were no basis for the allocations.
Here's a look at the series of events so far.
July 14, 1992
A number of coal blocks, which were not in the production plan of Coal India Ltd and the Singareni Collieries Company Limited (SCCL), were identified and a list of 143 blocks were prepared.
The Coal Ministry orders setting up of a screening committee to consider proposals from private power companies for captive mining.
1993 to 2010
As many as 70 coal mines or blocks were allocated between 1993 and 2005, 53 in 2006, 52 in 2007, 24 in 2008, 16 in 2009 and one in 2010.
In all, 216 block were allocated between 1993 and 2010, out of which 24 were taken away at different points in time, effectively leaving the total number of allocated blocks at 194.
A draft report by the Comptroller and Auditor General of India (CAG) accused govt of ‘inefficient' allocation of coal blocks 2004-2009; estimates windfall gains to allottees at Rs 10.7 lakh crore.
May 29, 2012
Prime Minister Manmohan Singh offers to give up his public life if found guilty in the scam.
May 31, 2012
CVC, based on a complaint of two BJP MPs directs a CBI enquiry into the case.
Allegations against several politicians and industrialists surfaces. Reports accused them of having benefited directly or indirectly from the coal block allocation process. The leaders include Subodh Kant Sahai, Naveen Jindal, S. Jagathrakshakan, Prem Chand Gupta and Ajay Sancheti.
Coal Ministry forms an inter-ministerial panel to review the process of allocation of blocks and to decide either on de-allocations or forfeiture of bank guarantees. The Government then took back about 80 coal fields while bank guarantees in 42 cases have been forfeited.
Final CAG, tabled in Parliament, tones down loss to exchequer figure to Rs 1.86 lakh crore.
The Supreme Court begins monitoring the CBI probe into the coal field allocations.
April 23, 2013
Slamming the allocation process, the Parliamentary Standing Committee on Coal and Steel, in a report tabled in Parliament, said that the coal blocks distributed between 1993 and 2008 done in unauthorized manner. It recommended that all those involved in the process should be examined.
April 26, 2013
Submitting an affidavit, CBI director Ranjit Sinha said that the investigation report was shared with then law minister Ashwani Kumar.
May 10, 2013
Following outcry over the issue, Ashwani Kumar resigned.
June 11, 2013
CBI filed first information report (FIR) against Naveen Jindal and Dasari Narayana Rao.
October 16, 2013
CBI registered an FIR against industrialist Kumar Mangalam Birla and former coal secretary PC Parakh.
Parakh in his book said that the authority of former PM Manmohan Singh was undermined by former coal ministers Shibu Soren and Dasari Narayan Rao. He said the two Ministers aided by industrialist Naveen Jindal, hasten the move to adopt the process of open competitive bidding for auctioning coal fields.
The Supreme Court sets up a special CBI court to try all coal field allocation cases.
The CBI decides to close its case against Birla and Parakh.