Which configuration or control object in SAP Financial Accounting should be used to prevent users from changing the reconciliation account field in a customer master record?

Introduction / Context:
In SAP Financial Accounting, reconciliation accounts link subledger accounts such as customers and suppliers to the general ledger. For data integrity, organisations usually want to prevent users from changing the reconciliation account field in customer master records, because such changes can break the reconciliation between subledger and general ledger. SAP provides several field status controls at different levels. This question asks which control object should be used to prevent changes to the reconciliation account field.

Given Data / Assumptions:
- The reconciliation account field exists in customer master records and determines which general ledger account is used for automatic postings.
- Several field status mechanisms exist: in account groups, posting keys, document types and general ledger master records.
- The goal is to stop users from changing the reconciliation account in customer master data once it is set up.
- The solution should be robust and work for all postings and activities.

Concept / Approach:
The reconciliation account field in a customer master record is controlled by the field status group of the corresponding general ledger account. When the field is set to display only in the field status group of the reconciliation account, users cannot change the reconciliation account in the customer master. Other field status controls, such as those in account groups or posting keys, influence which fields appear during document entry, not which reconciliation account can be assigned. Therefore, controlling the field status at the general ledger level is the correct approach for preventing changes to the reconciliation account in the customer master.

Step-by-Step Solution:
Step 1: Identify that the question focuses on preventing changes to the reconciliation account field in the customer master. Step 2: Recall that reconciliation accounts are defined in the general ledger and assigned to customer master records. Step 3: Remember that the field status group in the general ledger master controls how related fields behave in subledger masters and postings. Step 4: Review the options and look for the one that mentions the field status group of the reconciliation account. Step 5: Select that option as the correct answer.
Verification / Alternative check:
As an additional check, consider the scope of each control. Posting key and document type field status affect document entry, not the master data fields. Customer account group field status can hide or show fields at master record level, but it does not directly lock the reconciliation account if the general ledger field status allows changes. The field status group of the reconciliation account is the most specific control for this purpose and aligns with best practice recommendations in SAP documentation.

Why Other Options Are Wrong:
The field status of the activity (such as create or change) does not provide the fine grained control needed for a specific field. Posting key and document type field status apply during posting, not during master data maintenance. The customer account group field status can influence which fields are optional or required but does not fully prevent reconciliation account changes if the general ledger settings are open. Therefore these options do not reliably secure the reconciliation account assignment.

Common Pitfalls:
Many learners confuse the various field status options and may choose the customer account group because it is directly related to customer master data. Another pitfall is to think that posting controls alone are enough, forgetting that master data maintenance is a separate process. To avoid such errors, always consider where the field is technically controlled and how SAP recommends securing critical fields such as reconciliation accounts.

Final Answer:
You should use the field status group of the reconciliation account in the general ledger master record to prevent users from changing the reconciliation account in the customer master data.