The two million word report into the Iraq War should be ready for publication in June or July 2016.
Sir John Chilcot revealed the timetable in a letter send to David Cameron which is published today. The inquiry's chairman said the report would be published once it had been vetted.
But Cameron has told Sir John he is "disappointed" at the time table and urged him to "expedite" the final stages.
Sir John wrote: "My colleagues and I estimate that we will be able to complete the text of our report in the week commencing 18 April 2016."
At that time, confidential access will be given to a team of officials for National Security checking.
Sir John added: "I entirely understand that a checking process is necessary and is normal procedure in inquiries which have considered a large volume of sensitive material.
"I remain committed to producing a report that will meet the very wide ranging terms of reference we were given and reflect the considerable investment of time and effort by all involved."
By the time it is published, the report will have been seven years in the making, having been commissioned by Gordon Brown in 2009.
Last weekend Tony Blair apologised for “some of the mistakes” of the 2003 war. The former prime minister told CNN he regretted failing to plan properly for the aftermath followed the toppling of Saddam Hussein and the false intelligence upon which justification for the invasion was built.
“I apologise for the fact that the intelligence we received was wrong," Blair said during an interview with the broadcaster. "I also apologise for some of the mistakes in planning and, certainly, our mistake in our understanding of what would happen once you removed the regime."
Quizzed by host Fareed Zakaria if the invasion of Iraq was responsible for the rise of the Islamic State, Blair conceded “there are elements of truth in that,” adding: "Of course you can't say those of us who removed Saddam in 2003 bear no responsibility for the situation in 2015.”
Lib Dem leader Tim Farron, whose party opposed the invasion, said today: "The Iraq war impacted the lives of many, not least the soldiers who fought out there and their families. Given they have had to wait seven years for this publication, I urge the government and Sir John Chilcot to stick to this timetable. It is already many years too late
"I also encourage the government to take this opportunity not just to reflect on the choices of the previous administration in the run up to the war, but to ensure that similar mistakes regarding major foreign policy decisions are not made again in the future"