Clarification on export invoice in regards to gst

I export software services to the US, and get paid with bank transfer in USD to our account.

I do not purchase anything in the process, so pay no GST tax on supplies and don't claim back any input credit.

When I export the software and prepare the export invoice for the buyer in U.S. do I specify the "Taxable Rate" as 0% since exports are tax free?

Or do I have to pay 18% tax out of my pocket and then claim back the amount later?

Thank you for your help.