Before enabling Advanced Currency Management (ACM), it is critical to understand its permanent implications. Once enabled, ACM cannot be disabled, making it an irreversible change to the organization's data architecture. This is a primary consideration for any administrator. Additionally, while currencies can be deactivated, any currency added to the organization's list of supported currencies cannot be permanently deleted. This means careful planning is required for which currencies to add, as they will permanently exist in the org's metadata. These two factors represent significant, irreversible changes that must be considered.

B. Opportunities display amounts in the record's currency, the user's personal currency, and the corporate currency, not just the customer's localized currency.

C. Advanced Currency Management uses dated exchange rates, meaning historical reports use the exchange rate effective on the opportunity's close date, not the last dated rate.

1. Salesforce Help, Considerations for Enabling Advanced Currency Management. Document ID: 000385023. This document explicitly states, "After it’s enabled, advanced currency management can’t be disabled."

2. Salesforce Help, Manage Currencies. Document ID: 000384999. This document notes, "After you add a currency, you can’t delete it. However, you can deactivate currencies that you no longer use."