Industrial sales abroad fell 11.8%, while sales on the domestic market dropped 13.2%, the entity's statistical office said in a statement last week.
Sales of intermediate goods increased by 17% on the year, while sales of non-durable consumer goods added 7.4%. Sales of durable goods fell by 15.6%.
Sales of capital goods edged up 0.3% year-on-year in September, while sales of energy plunged 95%.
On a monthly comparison basis, the Serb Republic's industrial sales rose 6.3% in September.
The entity's industrial sales in the first nine months of 2019 fell 5.2% on the year.
The Serb Republic is one of two autonomous entities forming Bosnia and Herzegovina. The other one is the Federation.