Aug 23, 2018 - 11:20 PM
Consider that an applicant tracking system may not be able to read a single file correctly. An ATS processes resumes and cover letters into easily examined files. Hiring managers may not read an application that didn't scan.
For some companies, different managers read the cover letter and resume separately. They could send the single document to both parties, but if you make their lives more difficult, they won't think favorably of you.
Many online applications have separate upload boxes for the cover letter and resume. At best, the system won't allow you to upload one file. At worst, the hiring manager will decide you can't follow directions. You may as well keep them separate if companies are going to make you do it anyway.
The exception here is if the job listing specifically requests a single file. In that case, you should obviously combine the two documents.