In SAP Business One, versions 9.0 and greater there is functionality that allows users to create an A/R credit memo for sales taxes only.
 
Scenario:  Your business has charged a customer for goods sold along with the associated sales tax.  Later, the customer produces documentation showing their tax exemption status.  You now must credit the sales tax only back to the customer.
 
How To Issue a Sales Tax Only Credit Memo
 
Create an A/R Credit memo document.  Apply the appropriate customer.  (For a tax credit memo only, make sure the “Tax Only” column is displayed in the form settings.) In the line item, enter the Item, Quantity, unit price, tax code and make sure the Tax Only checkbox is selected.  Add the document.
 
See below for Item Credit and Service Credit memo.
 
Item Credit Memo
 

 
 
 Service Credit Memo
 
Create an A/R Credit memo document.  Apply the appropriate customer.  (For a tax credit memo only, make sure the “Tax Only” column is displayed in the form settings.) In the line item, enter the GL Account, tax code, Total and make sure the Tax Only checkbox is selected.  Add the document.
 
 

 
 
Outcome of the A/R Tax Only Credit Memo
By running the sales, tax report you can see that the credit of the tax amount has been applied.
 
 
Sales tax report