Thanks for replying.
@JeffSchwenk, I checked the Inv Tax Detail and Summary and both were empty and History Detail was OK.
@Shawn Slavin, unfortunately, the client didn't even notice till all was done. Quicker Clicker. I'd have loved it if they had just deleted and tried again.
Their invoice had three lines on it and all were accurate on the invoice, journal and history detail. The only issue was the bottom line. It has contaminated the Non-Taxable and Balance amounts in the files mentioned above.