Pardon my ignorance, I have lost access to my Odoo expert and need to rectify a mistake. Last year we sold enough in Washington State USA that we reached the threshold where have to bill and remit their sales tax. We are in Oregon and don't have to deal with such things usually. A customer was invoiced for a sale with no sales tax listed and the customer paid. We requested that they pay the missing tax. They require an issuance of a credit memo and submission of a corrected invoice whereupon they will then pay the difference. I tried to fumble around to get this done but failed. Is there is tutorial on this or would someone care to walk through it step by step for me? I would be truly grateful.