One can either source new ADRs by depositing the corresponding domestic shares of the company with the depositary bank that administers the ADR program or, instead, one can obtain existing ADRs in the secondary market. The latter can be achieved either by purchasing the ADRs on a US stock exchange or via purchasing the underlying domestic shares of the company on their primary exchange and then swapping them for ADRs; these swaps are called crossbook swaps and on many occasions account for the bulk of ADR secondary trading. This is especially true in the case of trading in ADRs of UK companies where creation of new ADRs attracts a 1.5% stamp duty reserve tax (SDRT) charge by the UK government; sourcing existing ADRs in the secondary market (either via crossbook swaps or on exchange) instead is not subject to SDRT.