If you are looking to sell products online using a large e-commerce distributor, you may be asked to obtain UPC codes for your products. What is often required nowadays is not just a simple UPS number, but rather a Global Trade Item Number (GTIN). This is a global product number that identifies the company as well as the product and it can be used globally.
To obtain a unique UPC:
Apply for a GS1 company prefix directly through GS1 US organization
Assign a unique product number to every variation of your product (size and color), most often 11 digits, GS1 may assign a 12 number as a check digit
Decide on how you will package your product and where your code will be displayed (retailer may have requirements for placement)
Place your barcodes and use these numbers to track your inventory