The online-only bank is now offering two- and five-year product transfers between 60 per cent and 90 per cent loan to value (LTV).
There are no product fees on the revised range.
Where possible, the lender said it will use the House Price Index to value homes to help speed up the process.
Customers whose fixed terms are coming to an end have been advised to contact their broker from home to arrange a transfer.
Atom said it does not believe products should be on sale where there is not a “reasonable chance of completing”.
As the government has advised buyers and sellers to delay moves until the Covid-19 crisis has passed, the bank has decided not to reintroduce purchase deals until restrictions are lifted.
David Castling, director of intermediary lending said: “Given the current climate we’re making these changes to ensure that our existing customers have a simple range of no-fee product transfers available so they can take a new product from the comfort and safety of their own home.
“We’ve taken a phased approach in order to reintroduce mortgage products as soon as possible. We’re continuing to assess the market in order to relaunch products to new customers when the time is right.”