Septic system installation services are treated as civil engineering or works contract services under GST. In earlier years, different ways of combining excavation, tank supply and installation sometimes produced different effective tax results for similar installations, which made it difficult for contractors and property owners to keep a consistent tax position.
After the September 2025 changes, most septic system installation jobs under SAC 995434 generally fall in the 18 percent slab with
input tax credit
. This standard rate applies where the contractor supplies labour and related material as part of a works contract, unless a specific notification grants concessional treatment for a particular type of public or social scheme.
The table below gives the latest GST rate for services under SAC code 995434.