R1 means paid on time, or within 30 days of due date.This is the highest rating possible.
R2 means the account is past due at least one payment period (usually 31 to 60 days).
R3 means 2 or more payment periods past due (usually 61 to 90 days).
R4 means at least 3 or more payment periods past due (usually 91 to 120 days).
R5 means at least 4 payment periods past due (usually 121 to 150 days).
R9 means at least 6 payment periods past due, or a write off after 180 days. This is the worst rating possible. Generally, it will create a negative entry in the Public Records/Collection section of a credit report in addition to the R9 reference in the Trade(lines) section IF the account has been sent to a 3'rd party for collection or sold to a debt buyer.
See the Equifax example below.
http://www.fcac-acfc.gc.ca/eng/resources/publications/budgetMoneyMgmt/CreditReportScore/ExEquifaxReport-eng.asp