At least in our agency- it will be converted to cash after a year.I thought that was universal, but I am not sure. This is the Federal government. Also you might not be paid at 1.5 of your current salary- there is a cap. I believe it is GS11, step 10. Thirdly, your supervisor is supposed to have you use comp time before you use any annual leave (to prevent pay out) and lastly, i have to have supervisory approval to work comp time- I cannot just decide to do it.