Invoice Printing

I currently have a dell 1320c printer.  Whenever a delivery is made i just print two copies of the delivery note (one for them to sign and keep and one for them to sign and give back to me).  My question is, is this the best/most cost-effective way to do it?  should i be using a dot matrix machine or some sort of carbon copy paper?  Im new to this and need to make sure im not throwing money or time away. 

Any help much appreciated