You can't.  Deleted is deleted.

But how I should understand that the Customer is deleted in Sage 300?
For example, during the first sync process, I received an active Customer and reserved it in my application.
Then, the user removed the Customer in Sage 300.
In this case, I cannot receive information that the Customer is deleted, because Sage 300 API returns only active Customers.

Could you recommend the was how to receive deleted Customers from Sage 300?

But how I should understand that the Customer is deleted in Sage 300?
For example, during the first sync process, I received an active Customer and reserved it in my application.
Then, the user removed the Customer in Sage 300.
In this case, I cannot receive information that the Customer is deleted, because Sage 300 API returns only active Customers.

Could you recommend the was how to receive deleted Customers from Sage 300?

I already told you.  Deleted is deleted, forget about it.

Thank you!