Deposit contribution w/out EIN?

Last minute request to set up a retroactive plan.

Upon requesting the Trust EIN, the site wouldn't process online so it will be done old school and they will mail out the EIN.

Assuming the EIN does not arrive prior to contribution deposit deadline (10/15), if the actual trust account cannot be formally set up, can the deposit still be formally made?

Use the employer EIN to set up the account and then update it when the TIN arrives. Been there, done that.