Invoice - Credit Sales

Hi, I have added a customer with payment term of 1 month credit. I have tried to issue invoice as follows:-

1) Direct Invoice - the system not allowed me to issue for credit sales, message [Customer's payment terms 'Due By End Of The Following Month' cannot be selected on this POS].

2) Invoice against sales delivery - the payment terms shown [cash only]. But actually i created the customer payment term was Due by end of the following mth.

The above situation caused me unable to issue invoice for my credit sales customer. If i used option 2 to issue invoice, it will automatically posted with customer payment, but actually the customer will only pay on the following mth.

Please help to advise how can i issue invoice for credit sales? Many thanks.

Regards,
elclim