You can probably download a template and fill & print it out for the purpose. Google: canadian invoice template.
BTW, do you have a GST/HST registration for your business? If you don't, you can register one online under your legal names within a few mins.
Thanks a lot for the instruction. I don't have any business registered. Is that necessary to have a business before sending any invoice?
Thanks again. The amount will not hit the threshold. Probably won't benefit from anythingI don't think it is mandatory. But, with it, you can benefit from it (such as GST credit), and the payer may also be able to claim 'certain things' from their side. Without it, you may just claim the whole amount you receive as part of your personal income.
For accuracy, I would recommend you to check CRA resources.