Assigning (your own) unique id to records on Google Sheets makes these transactions idempotent. Meaning that an transaction with a unique id cannot be recorded twice in the same book. Unique ids prevent creating duplicate transactions in a book.

Also, from the point of view of a book such a unique id (from a sheet or elsewhere) is a remoteId and is accessible via the REST API or the BkperApp (Google Apps Script). This makes tasks along a financial workflow beyond Bkper easy to automate.

Freeze the first row of your Sheet

Freeze the first row with the column Headers and besides the system properties insert an ID Column.

After freezing the first row go to the Bkper Extension and select the Generate Transaction IDs option.

The Unique IDs are inserted in each row that has data on it.