Instead of customer account, Expense GL should hit for Tax amount in FOC sales

Hi All

I have a below requirement.

We have a process which similar to FOC Sales.

Order-Delivery + Billing with net value 0 but Tax should be calculated on the Invoice but should not debit the customer account instead it should hit the some Expense GL account which company provide it. 

Since the product is sample customer will not pay but it is taxable and company should pay the tax to the Govt. Please let me know if you need any further details. by adding the R100 we are making the net value zero.

e.g. below 

I tried in Google to find out similar requirement post but did not find helpful solution to the above. Please share the link if the similar issue was discussed before in SCN.

Small edition to initial post. The accounting entry should be as below. Please let me if this can be achievable if yes, what setting needs to be done?

Thanks!