Southampton have agreed a fee with Arsenal for the permanent transfer of Aaron Ramsdale.
It is understood the fixed fee is £18m, potentially rising to £25m if performance-related add-ons are met.
Negotiations are continuing on the other aspects of the deal.
Arsenal have many of the details of a deal in place to sign Espanyol keeper Joan Garcia if and when Ramsdale leaves.
It is understood they are in a good position to close a deal.