Transactions should be marked "pending": true when they have been labeled as such by the institution. Transactions should be marked "pending": false when they have settled and posted.
When a pending transaction is converted to a posted transaction, Plaid removes the pending transaction, sends a TRANSACTIONS_REMOVED webhook, and returns the transaction’s new, posted transaction. The posted transaction should have a pending_transaction_id field, whose value is the transaction_id of the now-removed pending transaction.
It is worth noting that the pending and posted versions of a transaction may not necessarily share the same details: their name and amount may change to reflect tips and other updates. Pending transactions are short-lived and frequently altered or removed by the institution before finally settling as a posted transaction.
In some rare cases, it is not possible to match a posted transaction to its pending counterpart. On such occasions, the posted transaction will be returned without a pending_transaction_id field, and its pending transaction is removed.
Pending transactions are returned when possible, but are not available for all institutions.