VAT AMOUNT in lines of the Invoice

If I go to Purchase > Order Processing > Invoice, in the part of lines (Type, Number, Search Description, Location Code, Quantity, etc) I need to add an additional Field called: VAT AMOUNT, where I can get this option to add here?

click on subform press ctrl+f2 it will open designer click on show fields and then select tax amount field and add in subform

save the form thats it!