An accounting unit, when you are talking about financial accounting, is the word that described the assets and liabilities that are listed within the financial statements of the client.
This means that an accounting unit does not refer to the actual units that measure these assets and liabilities, but rather the assets and liabilities themselves.
These units should still be measureable, although this term does not refer to this specifically. The units will then be utilized in order to compare and to analyse the data, as they pertain to the task.
The accounting unit can also refer to the unit of measurement assumption. This assumption stipulates that a business is able to use the local currency as its unit of measurement when it undertakes the business of accounting.
For more information on the definitions used in accounting, watch this video: