Ter Stegen's deal is due to expire in two years and the new terms will see him defer a substantial part of his wage until further down the line to help the club create salary space for the season.
Barça are having problems registering all of their players within their LaLiga-imposed spending cap and deferring wages, in addition to moving players on, is one way of making room.
Ter Stegen, 31, also reached a similar agreement with Barça when he last signed a new deal in 2020 as the club grappled to deal with the financial affects of the pandemic.
During that time, he has made 378 appearances for the club, winning 15 trophies, including five LaLiga titles, five Copas del Rey and one Champions League.
If he fulfils the terms of his new contract, that would take him up to 14 years with Barcelona and close to Victor Valdes' appearance record for a goalkeeper at the club.
Ter Stegen is fourth behind Antoni Ramallets (384), Andoni Zubizarreta (410) and Valdes (536).