A primary care trust (PCT) in North Yorkshire had the biggest deficit of any PCT in England last year, official figures show.
The North Yorkshire and York PCT was £18.2m in the red in the year to March 2008, according to a report by the Audit Commission.
Its overspend was bigger than that of any other PCT and the fourth highest of any NHS organisation.
The trust said it was making savings and hoped to be debt-free by March.
The report shows that NHS finances have improved nationally, with only 11 out of 340 organisations, or 3%, reporting a deficit, compared with 22% in 2006/07.
PCT DEFICITS 2007/08
N Yorks and York - £18,226,000
Enfield - £13,308,000
Buckinghamshire - £11,574,000
Hounslow - £1,940,000
In January 2007 the North Yorkshire trust was the most overspent organisation in the NHS, with a £45m debt.
It cut services and shelved projects to make savings.
In March this year it said its main areas of overspending remained within contracts with its main providers.
Nicholas Steele, director of finance for NHS North Yorkshire and York, said the report's figures referred to the previous financial year and reflected the trust's finances at the end of the financial year in March.
He said the trust's financial position had improved since then, and it was operating with an overspend of £2.2m in September.
He said: "We have drawn up action plans to reduce expenditure in all areas to ensure that we do not overspend against this year's allocated budget.
"We will be working hard with our staff, contractors and partners over the next few months to achieve financial balance by the end of this financial year."
Mr Steele said despite the need to make savings the trust remained "fully committed to developing new, flexible services to ensure that our health care provision continues to meet the changing needs of our local population".