Establish continuous supply before choosing an invoice trigger
Under CGST Act section 2(33), continuous supply of services generally involves continuous or recurrent services under a contract exceeding three months with periodic payment obligations; the definition also accommodates notified services. A long engagement alone is not sufficient. For a qualifying supply, section 31(5), subject to the statutory qualification in section 31(3)(d), sets the invoice triggers according to the payment terms.
Read the applicable text: CBIC CGST Act, sections 2(31), 2(33), 13 and 31.
Build the calendar from enforceable terms
Where the payment due date is ascertainable from the contract, section 31(5)(a) requires issue on or before that date. Where the due date is not ascertainable, clause (b) requires issue before or at receipt of payment. Where payment is linked to completion of an event, clause (c) requires issue on or before completion of that event. Read the operative obligations and document which branch applies to each component; do not choose a later cash date for administrative convenience.
Keep completion evidence and payment evidence distinct
For milestone billing, identify the exact event and when it occurs. A certificate may evidence completion or itself be the agreed trigger; read the contract and keep dates of performance, certification and payment separately. For receipt-triggered billing, establish whether the amount is consideration, rather than a deposit not yet applied as consideration under section 2(31). Document changes to payment terms and approval rather than relying on an edited calendar.
Compute time of supply independently
The invoice trigger is a legal deadline; liability timing is tested under section 13. For ordinary forward charge, section 13(2) generally uses the earlier of timely invoice and payment. If the invoice was not issued within the applicable period, it generally uses the earlier of provision of service and payment. If neither limb applies, check the recipient’s book entry. For this test the supplier’s payment date is generally the earlier of its own book entry and bank credit. A payment can affect tax timing before a later invoice deadline, to the extent it covers the supply. Advance receipt documents under section 31(3)(d) and any eventual refund should be reviewed independently.
Reconcile cessation and period reporting
If supply ceases before completion, section 31(6) calls for an invoice when supply ceases, to the extent supplied before cessation. Preserve the termination facts and supported measure of work supplied. Build a monthly roll-forward of contractual due amounts, receipts, invoices, any advance adjustments and applicable return reporting so the same base is not counted twice.
Six worked illustrations
All facts and amounts are fictional. Calculations illustrate the stated assumptions, not a predetermined legal outcome.
Illustrative example 1: Fixed contractual due date
For a qualifying annual service, a ₹2 lakh instalment is due on 10 July 2026. An invoice issued 8 July is two calendar days before the section 31(5)(a) deadline, even if collection is later.
Illustrative example 2: Receipt where no date is ascertainable
A qualifying recurring contract has periodic payment obligations but no ascertainable date for this instalment. On the stated facts ₹1.4 lakh is received on 17 August and invoiced 19 August. The invoice is two days after the clause (b) trigger.
Illustrative example 3: Completion-based invoice
A defined event completes on 20 September; administrative approval is logged on 24 September and is not itself the contractual event. If invoiced on 24 September, it is four days late against the assumed clause (c) trigger.
Illustrative example 4: Partial advance before invoice
On a ₹5 lakh qualifying service instalment, ₹1.5 lakh is received in advance and documented. The remaining consideration is ₹3.5 lakh. Reconcile the advance separately when determining section 13 timing and avoid counting the ₹1.5 lakh twice.
Illustrative example 5: Cessation before completion
Assume an agreed ₹8 lakh total and evidence that ₹3.2 lakh relates to service supplied before cessation. If ₹2 lakh has already been invoiced against that work, reconcile ₹1.2 lakh still unbilled at cessation, before any separate dispute or valuation issue.
Illustrative example 6: Deposit later applied
A ₹90,000 refundable deposit is received and ₹25,000 is later applied as consideration. Under the assumed terms ₹65,000 remains unapplied and is not consideration under section 2(31). Analyse tax and document timing for the ₹25,000 applied as consideration.
Ten-step verification table
| Step | Action | Evidence |
|---|---|---|
| 1 | Read the signed service contract | Term and periodic obligations |
| 2 | Screen the definition | Duration, recurring service and notified scope |
| 3 | Split payment components | Contractual instalments and milestones |
| 4 | Select each invoice branch | Due-date, receipt or event evidence |
| 5 | Confirm actual milestone dates | Project records and certificate terms |
| 6 | Trace receipts and deposits | Bank, ledger and application evidence |
| 7 | Check invoice timing | Dated statutory document and exceptions |
| 8 | Determine section 13 liability timing | Invoice, supply and payment chronology |
| 9 | Reconcile cessation or advance items | Termination and advance-offset records |
| 10 | Review monthly output | Invoice register and return bridge |
Sixteen practitioner FAQs
1. Does exactly three months meet the duration limb?
The definition says exceeding three months; check any notified inclusion separately.
2. Does a long contract automatically qualify?
Check the continuous or recurrent nature and periodic payment obligations.
3. Can the invoice follow late payment if the due date is fixed?
The invoice is due on or before the contractually ascertainable payment date under clause (a).
4. When does actual receipt govern invoice timing?
Clause (b) applies where the due date is not ascertainable.
5. What if the contract defines an event rather than a calendar date?
Check whether payment is linked to completing that event under clause (c).
6. Is the certificate date always the event?
Use the actual contractual trigger and supporting evidence.
7. Can a back-office approval delay invoicing?
Not unless it is relevant under the actual operative terms and statutory branch.
8. Are goods covered by the same sub-section?
Continuous supply of goods has a separate rule.
9. Does early payment affect time of supply?
It can under section 13 even where invoicing is due later.
10. Is a refundable security deposit always payment?
Section 2(31) distinguishes an unapplied deposit from consideration.
11. What happens if work stops mid-contract?
Review the cessation invoice rule and measure the service already supplied.
12. Does a delayed invoice move all tax to the later period?
Apply the late-invoice branch of section 13 where relevant.
13. Can one contract contain different triggers?
Analyse the actual terms for each component and resolve conflicts.
14. How are amendments documented?
Keep authorised effective dates and the original and revised calendar.
15. Should a receipt already taxed be counted again on invoicing?
Reconcile the same consideration and applicable reporting treatment.
16. Does the billing calendar determine accounting revenue?
Apply the relevant financial reporting framework separately.