magento - show vat in report but not in frontend -

i want apply 20% vat. add 20% price every product.but want show 20% vat in report in admin. there way show 20% vat report in admin without applying vat in frontend.

vat = price * (vat percentage/100)

20% vat $120: $120 * 0.2 = $24

in product class have 1 property price excluding vat , property price including vat.