The phrase ‘supplementary comments’ is generally found on a job application form.
Most job applications ask for the usual details; your contact, your employment history, your experience, education and so on. There is often not enough space for the applicant to write in detail all their relevant qualifications/experience so employers may ask for additional information - they may phrase it in a general way like this.....
"...please add any supplementary comments which may be relevant to this position..."
Before you start, check out what you’ve already stated on the form and make sure you’re not duplicating what you’ve already said.
You may for example be involved in voluntary work which is relevant to this job and now is the place to mention this!
For example, if you are applying for a job working with children and you volunteer as a scout leader - this is where you would detail this as extra, non-paid but very valuable, experience.
Or you may have a hobby or interest that will enhance your application for this particular role. For example - you may be applying for a job as a computer technician and your are an amateur astronomer who uses technology all the time; a potential employer may be impressed by this!
Beware though, of detailing hobbies or interests that are not related to the position you are applying for. ‘I’m a DIY enthusiast’ is not particularly helpful if they are looking for a Kindergarten assistant!
Your ‘supplementary comments’ is also where you can show off your writing skills. Well crafted sentences, interesting vocabulary and good use of grammar will only help your application.
And please, please... if you are not a naturally good speller - get someone who is, to check it out; do not rely on your spellchecker- I have seen many resumes from reasonably qualified candidates rejected because the spelling was so appalling!
Take time and care over your ‘supplementary comments’ and it could make all the difference to your application and whether you get the job or not!