8. A computer for performing transaction-tax-related processing of a transaction, the computer being programmed to input, output or modify a transaction document having transaction-document lines with which one or more taxation levels are associated; the computer comprising: a processor to receive the transaction document and to perform the transaction-tax-related processing in response to the transaction document, wherein the transaction document includes data items representing transaction-tax-related information according to a data schema for representing transaction-tax-related information for different jurisdictions, including jurisdictions with different kinds and numbers of taxation levels; wherein the data schema provides a taxation-line entity for each of the transaction-document lines of the transaction document, wherein the transaction-document lines correspond to respective sub-transactions of the transaction; the data schema provides a taxation-line-item entity, related to the taxation-line entity, for each taxation level of a corresponding transaction-document line, wherein plural taxation-line-item entities are provided for the corresponding transaction-document line associated with plural taxation levels; and wherein an attribute of each taxation-line-item entity is used to indicate the taxation level represented by the taxation-line-item entity.
12. The computer of claim 8 , wherein the processor is to provide the transaction-tax-related information in a data file, and wherein the data file is a file of tokenized data.