Payment gateway callback URL

Hello,

Integrating a payment gateway with Woocommerce plugin, after clicking Pay on my site, i get redirected to payment gateway secure page for payment – one of the parameters sent to the gateway is the callback URL. After clicking Pay at gateway secure page, im redirected back to my site, ie. to the calllback url – this page then queries the gateway for the transaction result, and the gateway returns the result to the page.

My question is not coding/implementation related – rather its more on logic:
– Given above scenario, what would be the appropriate callback URL set as?? thinking of modifying the woocomerce thank-you template to use it. Again, I do not need to know how to code – rather just the appropriate location of the callback script.

Kindly advise please.

Thanks,
Edward