I recently had a paper accepted at an Elsevier journal, and am currently waiting for the typesetting process to start. Since it's open access there is a charge for publishing, yet I haven't seen where to pay. Does an email come after the typesetting process with details for payment or am I missing something?
Once your article is received by the production department, you should receive an email inviting you to complete the author forms (check your spam folder if you don't). One of these forms concerns the choice between the Gold Open Access option and the subscription model. Once you have made that choice and provided some additional information (mostly concerning if your research received US funding, directly or indirectly), the system will generate an invoice automatically.