Re : Invoice Error - No amount left

Hi

Please find below scenario

Po - 30 qty

Gr/Ir - 10 qty

Inovice - 10 qty

Later for remaining qty,

Gr/ir - 20 qty

Inovice  - 20 qty, at the time of posting invoice i'm facing this"No amount left to be invoiced for item 2 in currency NGN" error

Please guide

Thanks