Thanks for the information below and your suggestion. I agreed with option 3. However, in order to get rid of the test invoice, we need to cancel/credit it in the system.
Will it work if we write off the VAT on the credit memo to misc expense account code: 67970 (DR:67970, CR: Input VAT: 21910)?
Or would you suggest using AR adjustment account: 67830 instead of misc account: 67970?