A business over the threshold registers for a CRS identification number and reports GRT using the location code and rate for the place where goods or the product of a service are delivered (FYI-200 sets the exceptions). The official material read does not set a grace period between meeting the threshold and the start of collection, so the prudent reading is that registration and collection are due once the threshold is met; confirm the start date with the state before relying on any delay.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.