More than 3.5m applications have now been received for the EU settlement scheme, according to the UK Home Office.
EU citizens are asked to apply by June next year in order to carry on living and working in the UK after freedom of movement with the European Union ends.
The department said 3.56m was the best approximate up-to-date figure available and it was unable to give a specific number from the internal data calculations.
The news comes after last month immigration experts warned gaps in Government data were making it difficult to know whether the scheme is working.
According to official data published on Thursday, more than 3.4m (3,468,670) applications were received by the end of March.
This is slightly lower than previous estimates but the UK Home Office document said published figures “may not necessarily match monthly totals” as they are all experimental, meaning the exact numbers are provisional and yet to be finalised.
Some 493,800 applications were for children and 78,850 were from people aged 65 and over.
Northern Ireland had a “noticeably higher proportion” (18%) of applications from those under the age of 18 compared to the rest of the UK.
A decision has been made on more than 3.1 million (3,147,140) applications, leaving a backlog of 321,530 still to complete.
Some 58% (1,813,390) of concluded applications were granted settled status – giving them permanent leave to remain living and working in the UK – while 41% (1,299,350) were given pre-settled status, where they would need to re-apply again after living in the country for five years to gain permanent residence.
There have been 23,740 applications which were withdrawn or “void”, 10,030 classed as invalid and 640 refused, according to the figures.
Applications from British citizens – who already have a right to live in the country and would not require leave to remain in the country – are among those which would be classed as void, the UK Home Office said.