✅ What is “Source Document Number” in Service Tax? In the context of Service Tax returns (ST-3) and record-keeping, the “Source Document Number” refers to:
The unique number of the document based on which the service tax entry is made in your books — typically, it is the invoice number or bill number.
📄 Common Examples of Source Documents: Type of Transaction Source Document Source Document Number Service provided Invoice Invoice No. (e.g., INV/00123) Service received Bill from vendor Bill No. (e.g., SUP/0456) Reverse charge payment Self-invoice / challan Challan No. or Internal ref no. Service tax paid Challan (GAR-7 / now under NSDL) Challan Identification Number (CIN)
📝 Where It Is Used: In Service Tax Return (ST-3), you must report the taxable value, service tax paid, and reference documents (like invoice numbers).
The “Source Document No.” field captures the invoice or challan number against each entry.
⚠️ Tips: Always maintain sequential invoice numbers — it helps in audits and ST-3 reconciliation.
In the case of reverse charge, where you generate a self-invoice, the self-invoice number becomes the source document number.
🔚 Summary: Source Document No. = Invoice Number / Bill Number / Challan Number — depending on the transaction.