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).
Triggers [Cart merge during sign-in](/../api/customers-overview#cart-merge-during-sign-in).
If the Customer exists in the Project but the `stores` field references a different [Store](ctp:api:type:Store), this method returns an [InvalidCredentials](ctp:api:type:InvalidCredentialsError) error.
Authenticates a Customer associated with a Store. For more information, see Global versus Store-specific Customers.