Change invoice heading names

is this possible to change QTY from invoice to HOURS? and unit price to services?


The Qty label will change automatically if all items listed on an invoice are measured in the same units. If they are not, the Qty label remains and individual line items show their units of measure. But if you are recording time, use the Billable Time module, and entries will be labeled in hours automatically. Beyond that, you could change the heading in a custom theme, using a substitution filter.

Why would you want to convert Unit price to Services? The price is part of calculating the Amount field. Entering a service description or name there would make no sense at all.