Hospital bosses face a £1.5 million deficit following an action plan to improve services.
Eastbourne Hospitals NHS Trust has blamed "unprecedented financial pressures" for the shortfall.
The trust, which runs Eastbourne District General Hospital, will announce the situation to board members at a meeting later this week.
Alan Randall, trust chief executive, said much of the reason for the shortfall lay with the need to recruit nurses.
The recruitment drive was sparked by a damning report into levels of care following the death of a patient after a routine operation.
The report led to the resignation of the then chief executive, Clive Uren, and chairman, John Barkshire.
The hospital has since drawn up an action plan under new management which has led to more permanent nursing posts being filled and a range of other improvements.
Mr Randall said: "The shortfall is clearly bad news. It is due to a number of reasons.
"In particular, we have incurred some external expenses as a trust in getting waiting lists down and increasing the number of nurses on the wards."
Board members will be told of a recovery plan currently being developed in order to balance the books.
The trust aims to wipe out the debt in four years and says any shorter timescale could hit services.
A team of external consultants has been appointed to pinpoint where savings can be made and to outline efficiency plans.
Mr Randall said: "Ours is not the worst situation. There are hospitals that are facing much bigger problems.
"Eastbourne Hospitals has a very proud tradition of not getting into financial difficulties and we aim to maintain that.
"We are confident we can release money from other places to improve the situation."
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