MSI Installments

To our clients who are located in Mexico, Galileo offers an installments feature, which involves a type of credit called meses sin intereses (MSI) or "months without interest." With this feature, you can provide your cardholders with the option to pay off their purchases in multiple interest-free installments, when they shop at qualified points of sale. This feature is similar to Galileo's Buy Now, Pay Later product, except that it leverages the existing Mexican financial infrastructure and does not use virtual cards to pay the merchant.

According to Mastercard, “Customers want more from their money, with greater flexibility, security and control in how to pay.” With installments, your cardholders can have more choice of payment options to accomplish expectations.

That same report from Mastercard says that in 2022:

  • 64% of global consumers felt safer using an installment solution backed by a major payment network.
  • 37% of consumers increased their usage of installment plans.
  • For 2023, 47% of global consumers would like to use an installment plan.

With MSI Installments, you can offer your cardholders the possibility of paying in more than one installment for a purchase of any good or service, according to the merchant’s conditions, which can help with:

  • Increasing cardholder adoption
  • Increasing purchase volume
  • Differentiation by offering a new type of transaction
  • Meeting cardholders' expectations

Use case

It's late November, Christmas is coming, and your cardholder Eduardo needs to buy presents for his family. However, he does not have enough funds to pay for everything right now. He goes online to a qualifying store's website and selects several items totaling $9000 pesos. As he processes his shopping cart, the website asks him if he would like to pay all at once or in installments. The site shows the MSI Installments options, and he selects a six-month plan, which best suits his financial situation. He had $10,000 available credit before the purchase, and now his available credit is $1000.

During the next six months, Eduardo sends you $1500 per month, according to the terms of the installment plan. As each payment is processed, his credit limit increases by $1500 until he has paid off the entire purchase, and his credit limit is restored to $10,000.


You must meet these qualifications:

  • Your sponsoring bank is in Mexico.
  • You are offering Mastercard credit BINs.
  • You are the system of record for your program.
  • You consume the Auth API.

Initial setup

Implementation includes these steps:

  • Sign up with Mastercard for the MSI Installments program and select the qualifying merchants, which must be domestic to México and be able to pay through SPEI.
  • Mastercard then sends you a merchant list with the merchant IDs of qualifying points of sale.
  • Galileo sets product parameters and performs other setup tasks.
  • If you have not already done so, implement the Auth API.

MSI Installments process

This is a simplified description of the process behind MSI Installments. When the cardholder makes a purchase:

  1. The cardholder goes to a qualifying store to make a purchase, either in-person or online.
  2. When the merchant processes the card, the system presents your MSI Installments offerings, and the merchant asks the cardholder whether they would like to pay all at once or in installments.
  3. If the cardholder asks for an installment option, the merchant communicates that information in the authorization request.
  4. Galileo relays the MSI information to you with information from Mastercard in the Auth API webhook. The information is in advanced_auth_api_fields. For details, see MSI Installments data in the Auth API Field Detail guide.
  5. You validate the merchant ID against the merchant list that Mastercard provided. If the merchant does not qualify, you decline the transaction with response_code: 12.
    • If you approve the request, Galileo sends the BAUT: auth event message.
    • If you decline the request, Galileo sends the DAUT: denied_auth event message.
  6. When the settlement file arrives, Galileo sends you a SETL: setl event message.
  7. Galileo sends you a specialized RDF every day with settlement information from Mastercard.
  8. You process the settlements, including any charges to the cardholder.
  9. You inform Mastercard of qualifying transactions via a Mastercard API.
  10. You reconcile fees with the merchants via SPEI.

MSI Installments data

Galileo provides you with MSI Installments data in these ways:

  • A daily MSI Installments RDF that lists all of the installments-related transactions, including the contents of PDS0663.
  • In the Authorized Transactions RDF, the AUTHORIZATION RESPONSE field contains 12 for denied transactions. (However, if Galileo calculates another response code that takes precedence over 12, that code is returned to the merchant and is present in the RDFs. For example, if the account is not set up for MSI Installments, Galileo returns response_code: 57.)
  • In the Auth API webhook, advanced_auth_api_fields contains the values shown in MSI Installments data in the Auth API Field Detail guide.
  • In the response for three transaction-retrieval endpoints (Get Account Overview, Get Authorization History, Get All Transaction History), this string is included for MSI Installments–related transactions only:
   "code": "MEXCTA",
   "num_installments": "NN",
   "description": "Installments without interest"
   "grace_period": "NN"
  • In authorization-related events (BAUT: auth and DAUT: denied_auth), you have these new fields:
    • mc_promotion_code — Contents of DE048 SE95. For MSI Installments in Mexico this is always MEXCTA.
    • mc_installment_pmt_data — Contents of DE112 SE7
      • Positions 1–2 (type of credit)
        • 03 — Without interest for the cardholder
      • Positions 3–4 (number of installments)
        • NN — Numbers 01 though 99
      • Positions 5–6 (grace period)
        • 00 — No grace period
        • 01 — One month
        • 02 — Two months
      • Positions 7–9 (transaction currency code)
        • 484 — Mexican peso
  • In the settlement event (SETL: setl), you have this field:
    • mc_installment_detail — Contents of PDS0663, which has the same format as mc_installment_pmt_data