Majid had intended to retire from the trust on his 60th birthday in October, but the trust previously said he would stay in post for the Nottingham attacks public inquiry hearings before leaving in June.
"We did apply to charitable funds to pay for an open staff and partner leaving event, which many clinical and non-clinical colleagues from across the organisation, as well as local healthcare partners, were invited to," he said in a post to staff.
"In hindsight, I've listened to everything you said, and clarified the rules around this, and I accept this was not a good use of charitable funds.
"The executive team is personally reimbursing the full amount on behalf of all those who attended.
"I am grateful for colleagues speaking up about this, can absolutely understand your frustrations and would like to offer my apologies."