連絡 and 報告: passing on news and reporting progress
Compare contacting someone with news and reporting facts or progress.
Getting in touch and passing on news
連絡 is read れんらく and refers to getting in touch or passing on needed information. 「遅れるので、友達に連絡しました」 means that the speaker contacted a friend because they would be late.
「着いたら連絡してください」 asks someone to get in touch when they arrive. It does not specify a call, text, or other method unless one is stated separately.
Presenting facts and progress
報告 is read ほうこく and refers to presenting the results or progress of something. 「調査の結果を報告しました」 describes the completed act of reporting the investigation results.
「進捗を上司に報告します」 means reporting progress to a supervisor. However, 報告 is not restricted to supervisors; results can also be reported to participants or family members.
Separating contact from its content
「担当者に連絡して、結果を報告しました」 says that the speaker contacted the person in charge and reported the results. Contact describes establishing communication, while reporting characterizes what was communicated.
「連絡がありません」 alone does not specify which result report is missing. 「結果の報告がありません」 more specifically says that no report of the results has been received.
How do you make an everyday request for a brief message on arrival?
Show the answer and why
You can say 「着いたら連絡してください」. Arrival is the condition, and the sentence itself does not request a detailed written report.