How can I always places Sales Orders on hold for a customer?

Hi,

I have a client with the requirement to always place Sales Orders for a particular customer on C1 hold.

We had a situation as follows:

The customer has a credit limit of £1, but as there was an unapplied invoice for £5000, the AR open balance was -£5000 and new orders under £5000 were going on without going on hold.

Client would like to handle this customer in a proforma fashion so all orders go on hold irrespective of the Credit Limit/open AR balance.

Would this be deemed Prepayment processing and controlled by the Payment Instrument?

Is prepayment processing on/off by version of P4210? If on, would a non-prepayment customer go on hold?