GST/TDS Structure for AC Marketplace

Job ID: 40270961

Budget: ₹12,500 – ₹37,500 INR

Project Description
I am looking for a qualified GST and Income Tax expert from India who has experience in service aggregator / marketplace business models such as Urban Company.
Business Model Explanation:
We operate an online platform where:
Customers book AC repair services through our platform.
A service engineer visits the customer location.
The engineer identifies gas refill and/or spare parts replacement (capacitor, PCB, fan, etc.).
The engineer purchases required spare parts directly from the local market.
The engineer installs the parts at the customer’s site.
Important Clarifications:
Our platform does NOT stock any spare parts.
Our platform does NOT purchase spare parts at any time.
Spare parts are always purchased by the engineer directly from the open market.
We generate a GST invoice to the customer including:
Service charges
Gas refill charges
Spare parts cost
We charge commission from the engineer (for example 10%–20%).
The engineer may or may not be GST registered.
Clarifications Required:
When the platform does not purchase or stock spare parts, how can it legally charge GST on spare parts billed to customers?
Which accounting structure is legally correct in this case?
Composite supply model
Back-to-back billing
Pure marketplace / commission model
If we earn commission from engineers:
How much GST applies on our commission?
How much TDS may be deducted on our income?
Where does 2% TDS apply under Income Tax Act?
On payment to engineers?
On customer payment to platform?
Only on commission?
What is the safest legal and tax structure to avoid future GST notices or litigation?
What type of agreement should exist between platform and engineer to remain legally compliant?
Deliverables Required:
Legal explanation as per Indian GST law
Recommended accounting structure
Commission + GST + TDS calculation example
Sample invoice format
Basic draft structure of Platform–Engineer Agreement