To edit your cash transactions, tap Payments> select your Cash Register account > under Transactions > +View more > find the specific transaction.
Once you open the transaction, you'll see a detailed audit trail, as to who updated the transaction and when, alongside the original and changed values.
Within this screen you can change: category (change or add), receipt (change or upload), add tags, add note, VAT (change or add), edit transaction. All the changes you make are saved automatically and reflected in your Cash Register.