Hi,
settle in sales tax G/L account without using tax code .
You are doing MIRO for vendor invoice and why you are linking to settle in sales tax G/L account?
In MIRO- you handle tax code with tax as INPUT (nature)Tax but in Sales Invoice you have tax code as Output tax.
Better understand real requirement and test it with one line item in MIRO- then only think for testing with 500 line items!
Regards,
Biju K