As described in our Trading Rules, the “high bid limit” (HBL) order control limits how high a Buy Limit Order can be filled based on the last sale price or the current best bid price.
Currently, the HBL is calculated as follows:
If the current best bid price is < 95% of the last execution execution, then the HBL will be set to last execution price + high_bid_limit_percentage
Otherwise, HBL will be set to current best bid price + high_bid_limit_percentage
HBL will only be enforced for specific trading pairs. You can see which trading pairs have a HBL set by looking at the high_bid_limit_percentage field of our api.exchange.coinbase.com/products endpoint.
For example, high_bid_limit_percentage : 0.03000000 would represent a 3% high bid limit.