Is there a requirement from the Consumer Data Standards to correlate pending and posted transactions such that the Consumer/ Data Recipient doesn't end up with duplicate transactions?
No. This has been deliberately excluded from the standards as a requirement due to feedback from the banking community. This is actually stated in the standards in the description of the
status field which says: "Note that there is currently no provision in the standards to guarantee the ability to correlate a pending transaction with an associated posted transaction"
Standards - BankingTransaction