Conditional Offers to Buy (COB) are credit-checked using a 20% buffer on top of the high price of the US IPO's price range, which is published in the latest prospectus. For example, if the prospectus specifies the price range as $8.00 - $10.00 per share, a price of $12 per share will be used to determine whether the account can support the COB quantity submitted.
The higher COB price is used solely for the purpose of determining whether the account has sufficient funds to support the position. For credit-check purposes, Interactive Brokers assumes that you will be allocated your entire COB quantity at the IPO’s price range high plus 20% ($12 per share in the example above).
Regardless of the price used during submission of a COB, the account will buy any allocated shares at the Public Offering Price (POP) as determined by the underwriter(s).