Doctors in Horsham and Mid Sussex signed 35 fit notes on average every day in 2017, according to NHS figures.
The number was up compared to 2016 with GPs in the Clinical Commissioning Group (CCG) covering the area issuing 12,835 notes, an increase of 164.
People in work need a fit note, previously called a sick note, if they are off work for more than seven days. Up to that point they can self-certify that they are unwell.
Across England, 5.8 million fit notes were handed out in 2017. The most recent data, for December last year, shows that the highest rate for notes given to patients of working age registered with a GP was in Knowsley on Merseyside. The lowest rate was in Richmond in London.
Despite being called fit notes, most of those issued classify people as unfit for work. This was the case for 94% of the notes in 2017.
However, fit notes are also used to advise patients and their employers on getting back to work. This includes recommendations for an employee to make a phased return or work reduced hours or with limited duties.
The most common reasons that doctors signed people off work in 2017 were mental and behavioural disorders, particularly stress, and back problems.
Women were signed off sick more than men. They received 57% of the fit notes last year.