Good guide. One spot where this matters even beyond delivery is tax. In Canada the tax rate follows the buyer's province, so a mistyped postal code can drop the order into the wrong province and charge the wrong rate. Ontario is 13 percent HST and Alberta is 5 percent GST only, so the same $100 order totals $113 in Ontario and $105 in Alberta. TrueNorth API has a validate address endpoint that pairs with its calculate tax endpoint for exactly this flow, validate first so the province you resolve is the province you tax. A practical tip: treat anything below a full postal code match as a reason to ask the customer to confirm before you charge them.