At the end of last year I decided to change jobs. Unfortunately the new position was not what I had hoped for and I decided to go back to my previous employer after four months. How do I handle this on a resume? Do I have to include the job I was at for only four months?
No, you do not have to put the four-month job on your resume. Here's how I suggest you list that span of time:
Your Job Title, Name of Company, 2004-2006, 2006-present
(I used a starting date of 2004 only because I don't know when you actually started working for your current employer.) Notice that this technique is honest, although admittedly mysterious.
On your resume, you never have to refer to that mysterious span of time (2006, 2006), however, on the job application you must reveal the four-month job. Hopefully, by the time you fill out the application form you will have won the job interview and you'll have a chance to explain the short-term employment in person.
To see how others have handled this sort of situation, check out 22 Sample Resumes for Job Seekers Who Have Had Short-Term Jobs.
Good luck with it!