MIRO - Tax Amount Calculation Based on Gross Amount not on Base Amount

Hi SAP Experts,

We have a PO where the total gross amount is 15,000.00 (inclusive of12% tax).  Tax Amount is 1,607.14, and Net Amount (base amount) is 13,392.86.  As shown below:

After Goods Receipt (GR), we did MIRO.  When we did MIR7, parking of invoice, and ticked the “calculate tax,” the tax computed was based on total gross amount of 15,000.00 (15,000.00 * 12% tax = 1,800.00), as shown in screenshot below.  Tax amount (as per PO screen above) should be computed based on the net amount (base amount) of 13,392.86 (as shown above).  Please see screenshot below the result of the MIRO.

Kindly advise as to how MIRO can compute the correct tax amount when calculate tax is checked.

Thanks,

Matt