The National Assets Management Agency (Nama) is the Republic of Ireland's "bad bank", set up to deal with toxic loans after the 2008 property crash.
The UK's National Crime Agency (NCA) is investigating Nama's Northern Ireland deal after cash was transferred to an Isle of Man bank account.
Parties to the deal deny wrongdoing.
Northern Ireland's First Minister Peter Robinson holds a Stormont meeting with PIMCO, a California-based global investment company.
It is interested in buying Nama's Northern Ireland loan portfolio. The meeting is also attended by Frank Cushnahan, at the time a member of Nama's NI Advisory Committee and Ian Coulter, then managing partner at Belfast law firm, Tughans.
Northern Ireland's then Finance Minister Sammy Wilson makes the Irish government aware that two clients of the US law firm Brown Rudnick are interested in acquiring the portfolio. One of them is PIMCO.
Irish Finance Minister Michael Noonan replies to Sammy Wilson, saying the interested buyers should contact Nama.
Mr Noonan makes it clear any sale must be done on the open market.
Frank Cushnahan resigns from Nama's Northern Ireland Advisory Committee, citing personal reasons.
US investment firm PIMCO submits a bid for the Northern Ireland portfolio.  It wants a deal which would mean the portfolio not going on the open market, attracting other potential purchasers. However, Nama decides it must be sold to the highest bidder.
Nama appoints an international bank to drum up interest in its Northern Ireland portfolio auction, dubbed Project Eagle. Nine companies, including PIMCO, are approached.
As PIMCO is finalising its bid, it discovers a fee arrangement involving a £15m, three-way split between its lawyers Brown Rudnick, Ian Coulter and Frank Cushnahan.
PIMCO makes Nama aware of its concern and withdraws. The lawyers then transfer their services to another bidder, Cerberus Capital Management.  Cerberus representatives, including former US Vice President Dan Quayle, meet Peter Robinson at Stormont.
In the end, only two firms make offers to buy Nama's Northern Ireland loans portfolio.
The highest bid of £1.24bn - a fraction above the minimum reserve price - is made by New York investment fund Cerberus and is accepted. The other offer from Fortress is for £1.1bn, which is below the reserve.
Ian Coulter, managing partner of Tughans, resigns the Belfast law firm due to what is described at the time as an "internal matter".
Mick Wallace, an independent politician from County Wexford, tells the Irish Parliament (Dáil) that £7.5m fees paid to Tughans had been moved to an Isle of Man bank account, reportedly to facilitate a payment to a Northern Ireland politician or political party.
In response, Tughans confirms Mr Coulter had moved money without its knowledge, but added that it had retrieved it.
Mr Coulter says no politician was ever to have benefited. A police investigation begins, led by the UK National Crime Agency.
Stormont's finance committee also opens an inquiry into the deal. Mr Cushnahan strongly denies any wrongdoing.
Loyalist blogger Jamie Bryson gives evidence to Stormont's finance committee.  Using privilege, he alleges five deal-fixers had been due to share the Isle of Man money.
Mr Bryson alleges they are Peter Robinson, Frank Cushnahan, Ian Coulter, Andrew Creighton (a developer) and David Watters (an accountant).
Mr Robinson says the claim is "without one iota" of evidence. Mr Creighton and Mr Watters also issue denials.
First Minister Peter Robinson appears before the finance committee and again rejects the suggestion he was to benefit financially from the Nama deal.
He tells MLAs he was motivated to have meetings with interested buyers "in the best interests of the economy". He contests claims that Deputy First Minister Martin McGuinness had been kept in the dark about the deal.
Former finance minister Sammy Wilson describes the Stormont inquiry as "a Mickey Mouse exercise". He accuses the inquiry of being "incompetent and biased" and says it had not separated out fiction and prejudice from fact.
Former Sinn Féin chairman on the assembly's finance committee Daithí McKay resigns as an MLA after leaked Twitter messages suggest he "coached" Jamie Bryson ahead of the loyalist blogger's appearance at the committee.
Twitter messages leaked to the BBC show that on 17 September 2015, Mr McKay sent a direct message to Mr Bryson, telling him to follow the Twitter account of fellow Sinn Féin member Thomas O'Hara.
The following day, a direct Twitter message from Mr O'Hara tells Mr Bryson: "You may only get 10-15 seconds on this before Daithi as chair has to pull you on it so squeeze your best points on this into 1-2 lines and come straight to the point."
Another message from him said: "Keep it short if you can, when it's said it's said and its privileged. Will be a great finisher."
Mr McKay says his actions were "inappropriate, ill-advised and wrong", but denies coaching Mr Bryson. Sinn Féin suspends Thomas O'Hara.
Jamie Bryson says he will not take part in any investigation.
"I won't be cooperating with any investigation into who I talk to, who my sources are: they can throw me in jail first," he says.
The following week, members of the finance committee call for Finance Minister Máirtín Ó Muilleoir to stand aside while the Twitter exchanges are investigated.
Mr Ó Muilleoir was a Sinn Féin member of the committee at the time of Mr Bryson's evidence session, and was named in the Twitter exchange between Mr Bryson and Mr O'Hara.
Deputy First Minister Martin McGuinness insists that Mr Ó Muilleoir will remain in his position.
A BBC Spotlight NI investigation reveals Frank Cushnahan was recorded accepting a £40,000 cash payment from a Nama borrower.
The recording was made in 2012 at a time when Mr Cushnahan was still working as an adviser to Nama.
The payment was made by the County Down property developer John Miskelly during a meeting in a hospital car park.
Mr Miskelly said "payments made by me to any persons have been lawful".
Mr Cushnahan denied any wrongdoing and told Spotlight he would not be providing any further responses because of the ongoing National Crime Agency (NCA) investigation.
BBC News NI looks at the timeline of Nama's Northern Ireland property loans portfolio sale, which is now the subject of a criminal investigation.