When CryptFolio updates one of your accounts or addresses automatically, through an API key or public address, we update existing transactions, and leave other transactions alone.
If two transactions have the same reference, value, currency, and date, then we consider them to be the same - and we will update the transaction with any additional information available (e.g. fee).
Since different public explorers for addresses often have different times for a transaction (often differing by only a couple of seconds, based on when the explorer received and processed the transaction), we consider two address transaction dates to be the same if they are within 5 minutes of each other. Otherwise, the dates need to be within 1 second of each other.
This means that if a provider suddenly changes the reference, value, or date for a currency, you may see duplicate transactions in your account.
If you are importing transactions manually, you can configure how you'd like CryptFolio to treat missing transactions: by either leaving them (the default), or by deleting them.