The statement said the deal began in 2018 and had been slated to end last year, but was extended till the end of 2021.
SMIC was one of the Chinese companies placed on a blacklist by the US Government in September last year, with American firms required to obtain a licence from the Department of Commerce if they wished to sell products to the Chinese entity.
Two years ago, the US put pressure on the Dutch Government to cancel a licence issued to ASML to sell such a machine to SMIC, part of its efforts to prevent Chinese telecommunications equipment vendor Huawei Technologies from obtaining advanced semiconductors for its flagship smartphones.
ASML said the deal with SMIC was for older technology, known as deep ultraviolet lithography.
The ASML statement said: "A disclosure has been made by SMIC under Hong Kong listing rules regarding a Volume Purchase Agreement with ASML.
"This relates to an existing agreement for DUV lithography that was already entered into on 1 January 2018 and that would run originally until 31 December 2020 and which was extended on 1 February 2021 to be valid until end December 2021.
"The total amount of purchase orders under the VPA was completed in the past 12 months’ period from 16 March 2020 until 2 March 2021 – to an aggregate amount of US$1.2 billion. The VPA, including its extension, is not a material event for ASML.
"We understand that the transactions contemplated under the VPA constitute disclosable events for SMIC under the Hong Kong Listing Rules."