The payments, which total more than £600 million, will be distributed between April 9 and May 14.
Eligible members must have had a savings or current account or mortgage with Nationwide at the end of September 2024, and have made at least one transaction or maintained a balance of £100.
Nationwide CEO Debbie Crosbie stated the payment acknowledges members' contributions to the building society's financial strength, which enabled the merger.
This follows previous member rewards, including £100 payments to some members in 2023 and 2024, totalling more than £3.5 billion returned in member value since April 2023.