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Sadly, you won't be allowed to collect bank account details as it will violate our Terms.
Since you're not a Financial Institution as well, the exception we offer won't apply to you either.
If what you need to collect is specifically IBANs and bank account numbers, I'm afraid you'd have to find a provider that will allow you to do that, specially now that we are certified as a PCI DSS Level 2 Compliant Service Provider.
However, if you want to collect other info for payment purposes (e.g. card details), that will then be processed later, we offer several payment processors that will allow you to achieve that.
1. Here's the complete list of all Payment Processors we integrate with https://apps.jotform.com/category/payment_processing
2. Here's a great article that will help you decide which one to choose: Which-Payment-Processor-is-Right-for-Your-Business
3. And to enable Payment Authorization (collect payment details now and charge them later), here's a quick guide How-to-Enable-Payment-Authorization (note that this option is only available in PayPal, Stripe, Authorize.Net)