The South African Revenue Service (Sars) has done over 100 inspections of "cash and carry" businesses in Gauteng in the past month.

About half of the businesses inspected did not comply with Sars’ rules regarding registration, filing or payment.

"Sars is closing in on those who under declare on their tax liability, both individuals and companies. We encourage all taxpayers to ensure their affairs are in order and they are contributing their fair share towards the cost of running the country." commissioner Tom Moyane said in the statement.

The inspections of cash and carry businesses had seen several audit cases concluded, raising tax assessments for the past financial year by more than R600m.

"There is a significant risk of under declaration due to poor record keeping and high volumes of cash transactions in this sector," Sars said in its statement.

Registrations were now being conducted, with follow-ups on outstanding returns, collection of outstanding debt and further risk profiling for full audits where there was evidence of under declaration and collection of outstanding debt.