I complete around 35 CT600s per year, but most of them are extremely simple and probably take no more than about 20 minutes. I use Steven Tuckwell's CTPro, which does the job fine -- user friendly, inexpensive and adequate for most of my purposes.
The problem is that CTPro will only handle a CT600 (Short). Occasionally I need to file a full CT600: either because the company only has rental income, or is an investment company, or, in the most recent case has not commenced trading but has foreign-exchange gains. I am reluctant to present clients, particularly larger clients, with hand completed forms as they look unprofessional. I could invest in a more sophisticated program, and indeed looked closely at Digita's, but my feeling was that I'd probably need a couple of days at least to get up to speed properly, which is about as much time as I spend on CT 600s in a year. Also of course there is the question of added costs when CTPro handles 95% of my clients more than adequately.
There was a company which used to provide a program called HotDocs which provided a free CT600 form filler, but as far as I can see from googling it it no longer exists. Another possibility is online filing, but I have never registered for that, have a form that needs to be submitted urgently and I gather the registration process could take a week or more. Anyone know where I could find a form filler, or have another solution?