Triggers [Cart merge during sign-in](/../api/customers-overview#cart-merge-during-sign-in).
A Cart returned in the [CustomerSignInResult](ctp:api:type:CustomerSignInResult) has any invalid Line Items removed and is [updated](/api/carts-orders-overview#cart-updates) with the latest prices, taxes, and discounts. During these updates, the following errors can be returned: [MatchingPriceNotFound](ctp:api:type:MatchingPriceNotFoundError) and [MissingTaxRateForCountry](ctp:api:type:MissingTaxRateForCountryError).
If an account with the given credentials is not found, an [InvalidCredentials](ctp:api:type:InvalidCredentialsError) error is returned.
Authenticates a global Customer not associated with a Store. For more information, see Global versus Store-specific Customers. If the Customer is registered in a Store, use the Authenticate (sign in) Customer in Store method.