For existing customers I would conduct a due diligence review and establish a reasonable follow up time to receive the IRS acknowledgement letter (don't try to call IRS, they won't tell you anything).
For a new account customer, I would require the registration before establishing the account except for a very few exceptions (such as a known customer opening a new business and he can provide me a copy of the application). This would be rare and well documented.
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Life without Jesus is like an unsharpened pencil - it has no point.