If you want a career change with your current employer, its not a lot different from applying for a new job outside your existing organization, except that the people involved already know you and carry their own perceptions of your capability.

You have already identified the job you actually want but are you qualified to do it? Is it a realistic career option for you or should you be considering something else? How is your self-confidence? In other words, do you believe that you have the right levels of skills to move into the new job or do you need help convincing people that you are the right person for the job?

First of all you must be able to properly and adequately describe your skills, because even if you know there is some room for improvement, you have to be able to convince an interviewer that your work skills are up to the job.

In order to be sure you have what it takes, I suggest you do a little role-reversal. Put yourself in your boss's position and try to work out what it would take to convince him /her that you are at the right level to move your career with this employer into a new job.

What questions would you need to answer to satisfy your boss of your suitability?

Write down a list of a least 20 of the worst and best questions they might throw at you. Then work out your answers with scenarios describing the skills you are putting forward.

When you are ready, have you researched whether other people have managed to pull off a career change like this with the organization?

If so you are ready to approach your boss and you should make it clear that you are not trying to apply pressure or sounding as if you'll leave if you don't get your own way.

Tell your boss that you are committed to the business and you would like to advance your career with them, but that you see your career moving towards becoming a developer and that you would like an opportunity to discuss this a career change option.