How to recover sales tax on an invoice for an exempted customer

Hi, Receivables Guru
Please help us in this issue.

1 - We have a customer number 2883 and this customer is exempted from sales tax.

2 - We do not want to issue an invoice with out sales tax amount.

3 - So we issue an invoice for customer 2883 with amount 700.00 and sales tax 70.00 ( sales code 10 % ).

4 - The customer paid 700.00 which represents its purchased goods.

5 - We want to settle the amount 70.00 which represents sales tax amount and to be shown in sales tax register

How to do this ?

Thanks to advise  .

George