What is GST (Goods and Services Tax)?
GST (Goods and Services Tax) is India's comprehensive indirect tax on the supply of goods and services. Implemented on July 1, 2017, GST replaced multiple cascading taxes like VAT, Service Tax, Central Excise Duty, and Entry Tax, creating a unified "One Nation, One Tax, One Market" system.
GST is a destination-based consumption tax where tax is collected at the point of consumption, not production. It has five rate slabs: 0% (exempt), 3% (precious metals), 5% (essentials), 12% (standard goods), 18% (services/electronics), and 28% (luxury goods).
How to Calculate GST: Exclusive vs Inclusive
GST Exclusive (Add GST to Base Price):
When you have the net/base price and need to calculate final invoice value including GST:
GST Amount = ₹10,000 × 0.18 = ₹1,800
Final Invoice = ₹10,000 + ₹1,800 = ₹11,800
GST Inclusive (Reverse GST - Remove Tax from MRP):
When you have the MRP/final invoice value and need to find base price and GST amount:
Base Price = ₹11,800 ÷ 1.18 = ₹10,000
GST Amount = ₹11,800 - ₹10,000 = ₹1,800
CGST, SGST, IGST Breakdown:
- Intra-State (Within same state): GST split equally into CGST (Central) and SGST (State). For 18% GST: CGST 9% + SGST 9%
- Inter-State (Between two states): Full GST as IGST (Integrated). For 18% GST: IGST 18%
- Imports: IGST applicable along with customs duty and IGST cess if applicable
Input Tax Credit (ITC) Explained
Input Tax Credit (ITC) is the core mechanism of GST that eliminates the cascading effect (tax on tax). It allows businesses to claim credit for GST paid on inputs (purchases) and offset it against GST liability on outputs (sales).
How ITC Works:
- Input Tax: You purchase raw materials worth ₹10,000 + 18% GST (₹1,800). Total paid = ₹11,800
- Output Tax: You sell finished goods worth ₹20,000 + 18% GST (₹3,600). Total collected = ₹23,600
- ITC Claim: Net GST payable = Output GST - Input GST = ₹3,600 - ₹1,800 = ₹1,800
- Benefit: Without ITC, you'd pay full ₹3,600. With ITC, you pay only ₹1,800
ITC Eligibility Conditions:
- Must possess valid tax invoice or debit note
- Goods/services must be received
- GST paid to supplier must be deposited with government
- Return (GSTR-3B) must be filed
- Supplier must have filed their return (GSTR-1)
ITC Not Allowed On:
- Motor vehicles for personal use (except when used for business purposes like taxi, driving school)
- Food, beverages, outdoor catering, beauty treatment
- Goods/services used for personal consumption
- Construction of immovable property (except plant & machinery)
- GST paid under composition scheme
GST vs Old Indirect Tax System
| Aspect | Old Tax System (Pre-2017) | GST System (Post-2017) |
|---|---|---|
| Tax Structure | Multiple taxes: VAT, Service Tax, Excise, Entry Tax, Octroi | Single unified tax: GST (CGST + SGST + IGST) |
| Cascading Effect | Tax on tax (no credit for previous taxes) | Eliminated through Input Tax Credit (ITC) |
| Compliance | Multiple returns to Centre and State separately | Single online portal (GST Network) |
| Registration Threshold | Varied by state (₹5-10 lakhs for VAT) | Uniform ₹40L goods / ₹20L services |
| Inter-State Tax | CST 2% (no input credit), entry tax | IGST with full ITC available |
| E-commerce | No specific provisions, complex | Specific TCS provisions, simplified compliance |
E-Invoice Guidelines for GST
What is E-Invoice?
E-invoice is an electronic invoice generated through the Invoice Registration Portal (IRP). It provides a unique Invoice Reference Number (IRN) and QR code for authentication. E-invoicing is mandatory for B2B and export invoices for businesses with turnover exceeding ₹5 crores.
Who Must Generate E-Invoice?
- All businesses with aggregate turnover exceeding ₹5 crores
- Applies to B2B invoices, exports, SEZ supplies
- NOT applicable to B2C (retail) invoices
- Special Economic Zones (SEZ) units/developers mandatorily
E-Invoice Generation Process
- Create invoice in accounting software (Tally, SAP, etc.)
- Upload invoice JSON to IRP portal (directly or via GSP)
- IRP validates and generates IRN (64-character hash)
- QR code generated with invoice details
- Digitally signed invoice returned with IRN and QR code
- Auto-populated to GSTR-1 and E-way bill system
Benefits of E-Invoice
- Auto-population of GSTR-1 (no manual entry required)
- Real-time tracking of invoices by tax authorities
- Reduced errors through standardized format
- Faster ITC claim process (pre-populated for recipient)
- Integration with E-way bill system (one-click generation)
- Prevention of fake invoices and tax evasion
Common GST Calculation Mistakes to Avoid
Wrong GST Rate Selection
Using 18% GST for gold (correct: 3%) or 5% for electronics (correct: 18%). Always check HSN/SAC code on GST portal or consult CA.
Rounding Errors in Invoices
GST should be calculated on line items first, then summed. Don't round base amount before adding GST. Round only the final invoice total.
Claiming ITC Without Valid Documents
ITC requires valid GST-compliant invoice with supplier GSTIN, HSN/SAC code, and tax breakup. Credit notes, delivery challans don't qualify.
Incorrect Place of Supply
For services, place of supply determines if IGST or CGST+SGST applies. Goods: location of goods. Services: location of recipient (B2B) or supplier (B2C).
Late Return Filing
GSTR-1 due 11th, GSTR-3B due 20th. Late filing: ₹50/day penalty (₹20/day for nil return). ITC can be claimed only after supplier files GSTR-1.