Invoicing in QuantX Ops: Part Billing, GST, and Never Billing Twice
How an invoice is raised against a work order, why part billing is normal, and the arithmetic that makes billing the same work twice impossible rather than merely discouraged.
An invoice in QuantX Ops is always raised against a work order, because the work order is what the customer agreed to. You do not retype the amount — retyping an agreed figure is precisely how an invoice comes to disagree with the contract.
Part billing is the normal case
Very little real work is billed in one go. A retention is held back. A running-account bill goes in monthly. A customer releases payment in tranches. So when you bill a work order you can leave the amount blank to bill everything outstanding, or type a figure to bill part of it — and the rest stays available.
Why you cannot bill the same work twice
The naive guard is a flag: has this been invoiced? That works only while a milestone can be billed once, all at once. The moment part billing exists, a yes/no question is the wrong question.
So the guard is arithmetic instead. What has been billed against a line is the sum of every invoice line pointing at it, less every credit note. You may bill what has not yet been billed, and no more. Two ceilings apply at once:
- what is left on the specific milestone or line
- what is left on the work order as a whole, across every invoice raised against it — including ones raised by hand, outside the schedule
The GST split is computed, not typed
You never choose between CGST+SGST and IGST. Place of supply comes from the customer's own GSTIN — the first two digits of any GSTIN are the state code. Same state as the site raising the invoice, and it is CGST and SGST; different state, and the whole amount is IGST.
| Customer state | Seller state | Result |
|---|---|---|
| Telangana (36) | Telangana | CGST + SGST |
| Maharashtra (27) | Telangana | IGST |
| Karnataka (29) | Telangana | IGST |
That matters because it is the number which has to agree with your return. A human choosing it from a dropdown gets it wrong occasionally; a rule reading the customer's own registration does not.
Issuing is the point of no return
A draft invoice is not in your accounts. Issuing it records the sale, the tax you owe and the money the customer owes you, in one transaction. After that it is never edited — see credit and debit notes.
Related: GST in QuantX Ops.
References
- E-Invoicing Rules in India: guidelines and turnover thresholds — Tally Solutions