It sounds very natural as it is. I wouldn't change anything. I suppose it would be a bit more informal to say, "When you apply for a job, your knowledge of English is always considered." But, even so, I like your original sentence better.

I agree with Devin in that the sentence is very well formed and sounds very natural as it is; however, it does not sound informal. If you specifically want to know how to say it in a more informal way (as in one friend speaking to another), I would say it more like: 1) When you apply for a job, they always want to know how good your English is. 2) When you apply for a job, they always look at your level of English.

Thank you for your excellent ideas, Shawn.

Agreed. It is already very natural sounding. :) Other informal ways to say this are: 1. When you apply for a job, your English skills are always taken into consideration., 2. They always look at how proficient you are in English when you apply for a job., 3. Your English skills are always considered when you apply for a job., 4. Interviewers always look at your English skills when you apply for a job., 5. Interviewers always consider your English skills when you apply for a job., 6. Companies are always interested in the English skills of job applicants., etc., etc. :)