See Create Payable Item for a detailed explanation of how to create payable items. This endpoint accepts the exact same parameters, just in bulk form.

This endpoint is atomic!

In order for any payable items to be created via this endpoint, all required validation checks must succeed for ALL items. If any validation checks fail, you'll receive an error message, and no changes will be saved.

That means this endpoint operates "atomically", and will either succeed for all items or fail for all items. It's not possible for this endpoint to succeed partially, where some payable items are created and some aren't: it's all or nothing.