The Waitangi Tribunal says it received up to 1000 Treaty submissions on Monday, leading up to its midnight deadline for claims.
Overall, it received about 2000 submissions since 1 August - 1 September at 11.59pm.
The Government set a deadline of 1 September in 2005 for claims to be lodged, with the aim of resolving them all by 2020.
Director Darrin Sykes says 10 staff processed claims sent by email and fax on Monday night.
Only five submissions arrived after the deadline, with three arriving by fax on Tuesday morning.
Mr Sykes believes they could have been double-copies of submissions which were earlier sent to the office within time.
On Wednesday staff will begin planning how to handle the first stage of processing the claims, working towards the Government's aim of resolving all claims by 2020.