If you are at base rate or at a surcharge when the claim happens, you have the base rate rule: No matter how high your surcharge is before the claim, after 3 years you will go back to base rate (assuming no more new additional claims).
For example, lets say your at base rate (0%).
You get into 1 accident:
Today:+6 steps = +6(75% surcharge on "no discount" premiums)
Next year: = +5(55%)
Year after: = +4(40%)
Year after that: = base rate (0%).
If your are -6(30%) discount and 1 claim happens...
today: +5 steps = -1(5%)
Next Year: -2(10%)
Year after: -3(15%)
Year after that -6(30%) recovery rule (also assuming no new additional claims)
The claim does not disappear, it stays on your record for 20 years.
http://www.icbc.com/autoplan-insuran...-costs/crs.pdf