More than 3.5 million applications have now been received for the EU settlement scheme, according to the 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 3.56 million 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 3.4 million (3,468,670) applications were received by the end of March.
This is slightly lower than previous estimates but the 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There have been 23,740 applications which were withdrawn or “void”, 10,030 classed as invalid and 640 refused, according to the figures.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 Home Office said.
Refusals are made on eligibility or suitability grounds.
Applications are refused when someone is a serious or persistent offender or when someone does not meet the criteria for the scheme – if they are not living in the UK or are not from one of the countries which can apply.
But it may also be when insufficient proof of residence has been provided.
Overall, the highest number of applications continued to be from Polish, Romanian and Italian nationals.
Ealing, west London, had the highest number of applications from Polish nationals (16,630) of all local authorities.
Newham, east London, was the local authority area which saw the most applications submitted by residents (84,950).
Outside of London, the highest number came from people living in the Midlands – Birmingham (71,790) followed by Leicester (55,930).
Campaigners have called for the scheme’s deadline to be extended because of delays caused by the coronavirus outbreak.
Documents could not be accepted by post, scanning facilities and a helpline for applications had closed, and charities were unable to meet applicants needing help and advice in person during the pandemic, the Commons Home Affairs Committee heard last month.
The Home Office has since said the helpline is now back up and running.
In March, the number of applications being submitted and finalised each dropped by more than 100,000, showing the lowest monthly totals since June last year.
But Home Secretary Priti Patel told MPs the scheme was a “success” and she saw no reason for an extension as there is still just over a year left to apply.
She insisted support for applicants had not stopped and the Home Office was still receiving around 2,000 applications every day.
Announcing the latest figures, immigration minister Kevin Foster described the scheme as “the biggest of its kind in British history”, adding that there was “still plenty of time left to apply”.