PaymentInput a payment takes (the account, the variants or an inline plan, the promo code) plus where the buyer is: address, shipping_address, tax_ids and ip_address. Tax is calculated for the shipping address, else the billing address, else the IP address, and located_by says which one priced it. A seller who collects no tax on the purchase needs no location at all.
A quote is priced once, in the plans’ own currency, and expires at expires_at; quote again whenever the cart, the promo code or the address changes. A quote located by ip_address is an estimate: show it, then quote again with the buyer’s address. tax_status says whether every line was priced (calculated), whether the seller collects no tax on this purchase (not_applicable), or whether tax could not be priced (unavailable: quote again).