Avoiding transaction duplicates

After you make an API call to retrieve account's transactions, GoCardless requests transactions from the bank and cleans the output from duplicates before presenting the final response to you. If you see internalTransactionId field in the transaction output, this means that this specific institution's transactions have been cleaned of duplicates by GoCardlesss while still recognising valid duplicates - same-day same-amount transactions devoid of other distinguishing data points that would have been filtered out as instances of the same payment. You can learn more about this functionality in this article: internalTransactionId - a unique transaction ID now generated by GoCardless

It is vital to note that

• We re-fetch pending transactions from the bank every time you make a request for account's transactions. This means that the information on pending transactions might change. We would advise taking this into account and using pending transactions with caution, keeping in mind that these are for informational purposes only and that the information might be subject to change. 
  • If the bank returns duplicated transactions from their end (either booked or pending), the transactions will also be duplicated in GoCardless output. If you notice such cases, please let us know. 
    Also, to make sure that any possible transaction duplicates don't affect your services, you could implement a handling logic for such cases on your end. The best way to avoid storing duplicates is to take multiple data points or the whole transaction information into consideration.