Change text of purchase order field on sales invoice

I don’t need the purchase order field on sales invoice.
Is there a very easy way to change the text to read as ‘Speedo’ ?

If you don’t enter anything in that field, it won’t show on the sales invoice. If you are trying to use that field for something else, you will have to create a completely new view template. That, of course, requires HTML/CSS skills.

Sadly, you can’t just modify the default example view template that appears if you create a new one, because much of the functionality of the sales invoice will be lost.

Thank you for a very concise reply. I do not have HTML/CSS skills so things will have to remain like they are until I can give further thought to the matter.

Could you use custom fields?

Thanks Tut. I probably can but am unsure as to how to use them. And would it then show on a report?
This is a new client and we record the speedometer readings of the vehicles when they come in for MOT/service/repair.

You should be able to add this field as part of the sales invoice or as an element of an individual sales invoice item. See the Guide at When you create one, you have the option of specifying a position. I confess I don’t know exactly how you would position the field or just how much control you have over it, because I’ve never done that. But try it out.