Reviewing this dispute....customer notifies bank in writing 12/11/19 of unauthorized card transactions. The transactions are from various sources and some began as long ago as 10/2018.

Here is a breakdown of the disputed transactions along with dates and amounts:
"ABC Company" initial transaction was 10-12-18 for $20.00 (included on 10-26-18 stmt.), and has occurred monthly from Oct 2018 to Nov 2019.
"1234 Inc." – initial transaction was 2-22-19 for $5.00 (on 2-27-19 statement), again this has occurred monthly since Feb 2019 to Nov 2019.
"XYZ LLC" – initial transaction was 12-10-19 for $4.00 (on 12-27-19 statement),
"567 Corp" – initial transaction was 12-11-19 for $2.00 (on 12-27-19 statement).

We are a mastercard branded bank, and so zero liability comes into play....but under Re. E the customer must notify bank no later than 60 calendar days after statement, where the error FIRST appeared in order to receive provisional credit, correct? So would we owe provisional credit for only the XYZ LLC and 567 Corp transactions?

Can anyone share their thoughts with me on this?

The total amount disputed is $31?

No, customer is disputing all monthly charges from "ABC" (since they first began in Oct. 2018) at $20 per month, so $280 disputed from this merchant, and the same with "1234" customer is disputing all monthly charges (since they first began in Feb. 2019) at $5 per month, so $50, plus the two charges from "XYZ" and "567" so total is $336.00.

Reg E would hold the customer liable for a significant number of those charges under section 1005.6(b). Is there a lost or stolen card involved here? Doesn't seem so (perhaps compromised card info, though).

I believe Mastercard conditions its $0 liability coverage on the customer's attention to the account. Based on what you've shared with us, I don't think you have to honor the MasterCard $0 liability provision for these transactions.

Sorry - obviously I glanced over it and only saw the numbers with the $ amount in front of them. I agree that you would only be required to provide provisional credit for the transactions that occurred within 60 days from the first statement they appeared. THe older ones do not require provisional credit.

Back up a bit. The provisional credit provision is in 1005.11 and that only applies if the dispute is started within 60 days of the statement on which the disputed transaction appeared, period (not from the first statement on which the transaction appeared).

So, if this customer first made his claim on December 19 (I assume that he didn't make an earlier oral claim), any transaction appearing on a statement sent more than 60 days earlier (October 20) would not have to be included in the provisional credit.

Yes, card number was compromised.

OK. That still does not trigger the $50-two business day liability rule in 1005.6(b)(1), which is triggered when the cardholder becomes aware that the accepted access device has been lost or stolen. So only the liability limits under 1005.6(b)(2) and (3) will apply.