[ARCHIVE] Direct debit deduplication

Archived 2022.12.11. Content moved to Guidance on direct debits 

Question

How should the 'last' direct debit authorisation be selected from a set of transactions? There may appear to be multiple debits for a particular merchant, with different amounts at different times,  and directed at different account numbers and BSBs with their associated financial institution.

Should the list of direct debits be deduplicated by Merchant name only, or by a combination of merchant and financial institution, or also include the account and BSB which are held by us, but are not shared in the Direct Debit API responses?

An example set of transactions may be (data for illustration only):

Txn	Merchant	Amount	Date	Fin.Inst (FI)	Acct #	BSB
1	Telstra	25.99	1 Jan 2021	NAB	123	456
2	Telstra	31.00	5 Jan 2021	NAB	789	456
3	Telstra	17.00	7 Jan 2021	NAB	789	456
4	Telstra	47.00	7 Feb 2021	NAB	111	321
5	Telstra	47.00	7 Mar 2021	CBA	333	222

Answer

The 'last' direct debit is meant to indicate the most recently identified direct debit transaction. If the same merchant is debiting two accounts, they should be treated as two different direct debits.

Within an account, merchant is the determining factor. If a merchant debits the same account multiple times but from different Financial Institutions (FIs) it should be treated as a single direct debit.