A significant number of child refugees will arrive in the UK from the migrant camp within days, the BBC understands.
Officials have been focusing first on unaccompanied minors who have the right to join relatives under EU legislation.
A separate registration process will take place for vulnerable children who do not have family in the UK.
Under EU-wide regulation, asylum claims must be made in the first safe country a person reaches, but children can have their claim transferred to another country if they have family members living there.
The Dubs Amendment to the Immigration Act, originally put forward by Labour peer Lord Dubs, also requires the government to arrange for the transfer to the UK and support of unaccompanied refugee children from Europe.
Operating out of a recycled shipping container within the Calais camp, Home Office officials have been working with their French counterparts to register the children.
Home Secretary Amber Rudd has said the government is moving quickly and that she wants as many children as possible brought to the UK before the camp is shut down by the French authorities.
However, the charity Safe Passage, which is working alongside the government, says it has not yet been shown any operational plans setting out how the children will be transferred.
Britain is expected to take more than 300 children in total.
The Local Government Association has said that councils will require "long-term funding arrangements from government so that the commitment to support those children starting a new life in the UK is properly funded".
Meanwhile, French Housing Minister Emmanuelle Cosse has said the camp will be dismantled "when all the conditions for success are in place," Agence France-Presse reported.
The news agency quoted the minister as saying that it was "out of the question to leave these people living any longer in that mud and that distress", adding that another winter in the Jungle was "impossible".
It comes after aid groups asked a French court to delay the closure of the camp, arguing that the authorities were not ready to relocate refugees.
French President Francois Hollande has already said the camp will be removed by the end of the year.
He has promised to set up "reception and orientation centres" to take in asylum seekers.
A "dignified welcome" would be given to people who filed for the right to asylum but anyone who was unsuccessful would be deported, he said.