Tax Year Prior to 2020: What percent can I deduct on phone,Internet for each of my 3 rental properties

[KarenL2]

That's going to be different for everyone because it depends on your usage.  There isn't a "standard" amount to deduct.  The simplest option is to figure out how much of your time, on the phone and internet, is spent working on your rental properties and then divide it by 3 and apply the amount to each.