If one of your business bank accounts isn't showing, it's likely because the financial institution where you hold that account is not currently participating in Experian's CATO scheme. Capitalise can only display the data that Experian receives from participating institutions.
It is not possible for you to directly add a missing bank account to your Experian credit profile through Capitalise. The bank account information displayed on your Capitalise credit profile is sourced directly from Experian, primarily through the Current Account Turnover (CATO) scheme. This scheme relies on financial institutions (banks) to report account data to Experian.
Unlike Open Banking, where you can grant direct access to your account data, the CATO scheme (and the CAIS scheme for credit accounts) operates on a provider-driven model. This means that only the bank or financial institution holding your account can contribute this information to Experian.
What actions can you consider?
Enquire with your bank: you could consider contacting your bank directly to enquire if they participate in Experian's CATO scheme. If they don't, you could express your interest in them doing so, although their decision to join is ultimately theirs.
Consider financial institutions that contribute: If having a comprehensive view of your bank account data on your credit profile is important to your business, you might consider working with financial institutions that are known to contribute to the CATO scheme.
In short: you cannot manually add a missing bank account to your Capitalise credit profile. The reporting of this data is solely managed by the financial institution through Experian's CATO scheme. If an account is missing, it's because your bank is likely not a participant in this data-sharing initiative.