The collection of certificates of chronic illnesses before leave is taken is repeated every year. As a chronic asthma sufferer, I went to my GP who charged me EUR 15.00 for the certificate. I have a chronic illness, is it then worth carrying a certificate for 1 day of additional annual leave if I have to pay for it? The certificates could be permanent or at least for a longer period, as the doctor knows at least approximately what type of chronic illness it is and how long it is expected to last, based on specialist opinions.