Hi Louise,
I think you're referring to "Pre-authorized Debit (PAD)" where your client is taking money out of other people's bank accounts.
This functionality is available on a custom development basis for Adagio Invoices. Contact Steve Wilson in our office for pricing.
It has to be a custom project as your client's bank will not talk to us unless we are working on behalf of a client of theirs.
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Andrew Bates