Invoicing That Produces the Right Document the First Time, Every Time
GullySystem engineers the invoicing side of your software so GST documents come out correct: tax worked out by place of supply, IRN and QR code from the portal, e-way bills raised with the vehicle details, credit notes linked properly, and figures that reconcile with Tally. Filing stays with your CA.
- Built with your CA in the room, not around them
- Every rule traced to a document your accountant can check
- We engineer the invoicing. Your CA files the returns
We engineer invoicing into software for distributors billing across state lines, manufacturers moving goods under e-way bills, service companies dealing with reverse charge, e-commerce brands handling returns and credit notes, and exporters raising invoices without tax under bond. The common problem is never the tax rate. It is place of supply on a branch delivery, an item master with no HSN code, and a sales register that refuses to agree with Tally at month-end.
Does Your Software Produce a GST Invoice Your Accountant Does Not Have to Correct?
CGST and SGST Charged on an Interstate Sale
The customer master has a Karnataka address, the goods went to the buyer’s Hosur branch, and the software split the tax the way it always does. The buyer refuses the invoice, and the credit note and re-issue eat two days.
Items in the Master With No HSN Code
Someone added twelve products during a busy week and skipped the code because the field allowed it. Those invoices are now raised, printed and sent, and the gap surfaces when the returns are being prepared.
The e-Way Bill Raised on a Different Portal
Invoices come out of the billing software, then the same details are typed again into the portal for the e-way bill. The invoice number does not match, the vehicle number is entered wrong, and a truck waits at a check post.
The Sales Register Never Agrees With Tally
Billing says one figure, Tally says another, and every month-end someone hunts for the difference. It usually turns out to be rounding, a cancelled invoice that was never reversed, or a credit note posted against nothing.
Returns Handled by Editing the Original Invoice
A customer sends goods back and someone simply changes the original bill. No credit note exists, the invoice series has a gap in it, and nobody can reconstruct what was actually supplied that month.
Advance Received Against an Order Nobody Recorded as a Receipt
Money arrives before the supply, gets entered as a plain payment, and the tax treatment is worked out months later by an accountant reading a bank statement.
The Invoice Prints, But the Fields Are Not All There
A format copied from an old template is missing the place of supply, the reverse charge indicator or the correct series. It looks like a bill. It is not a document your buyer’s accountant will accept without argument.
Getting GST right is not about knowing the rates. It is about the software applying the right rule at the moment of billing, carrying the same numbers to the portal and to Tally, and refusing to raise a document that is missing something.
The Rules Applied at Billing, Not Corrected Afterwards
We work through your actual transaction types with your accountant, then build them into the invoicing: how tax is determined, which series applies, what a document must contain before it can be saved, when an IRN is required and when an e-way bill is. Portal calls happen from the same record that printed the invoice, and the same figures post to Tally.
Place of Supply Decides the Tax
The software works out the supply position from the ship-to state, the type of supply and the registration, so an interstate delivery to a buyer’s branch is not taxed like a local sale.
One Record, One Set of Numbers
The invoice that prints is the invoice that goes to the portal for the IRN and the same one that posts to Tally. Nobody re-types details into a second system.
Validation Before the Document Exists
Missing HSN, a GSTIN that fails its check, a blank place of supply or an unpriced line stops the save. A bill you cannot raise is cheaper than a credit note you have to issue.
What Changes When Invoicing Is Engineered Properly
Focus on business value before discussing technology. Here is what your team accomplishes in week one.
Fewer Invoices Coming Back
Tax determined from the ship-to position rather than the billing address, so the buyer’s accounts department stops rejecting bills and asking for a re-issue.
IRN and e-Way Bill Without a Second Portal
The IRN, the QR code and the e-way bill are raised from the same record that made the invoice, with the numbers carried over rather than typed again at a keyboard.
Bad Documents Are Stopped at Entry
The gaps that ruin a return, missing codes, failed GSTIN checks, an empty place of supply, are caught while the customer is still at the counter and can be settled in a minute.
The Sales Register Ties to Tally
Ledger-wise and tax-wise figures agree day by day, so month-end stops being an investigation and the differences that do appear have a reason attached.
Credit Notes Linked to What They Reverse
Returns and rate corrections produce proper documents against the original invoice, so the month can be reconstructed and the series has no unexplained gaps.
Your CA Gets Data Instead of a Puzzle
Extracts in the shape the returns need, with the exceptions listed separately, which shortens the argument between your office and your accountant every month.
What GST and e-Invoice Engineering Includes
Everything required from operational discovery to production deployment and long-term maintenance.
Transaction Mapping With Your Accountant
Every kind of supply you make written down and settled: local, interstate, branch transfer, job work, export, reverse charge, exempt and composition purchases, with your CA confirming the treatment.
Tax Determination Logic
Rules built into the software that decide CGST and SGST against IGST from the place of supply, the registration and the supply type, instead of leaving it to whoever is at the billing screen.
Invoice Format and Mandatory Fields
Print formats carrying the fields a tax invoice needs, with separate formats for a bill of supply, a delivery challan, a debit note and a credit note rather than one template edited by hand.
Item and Party Master Cleanup
HSN and SAC codes filled and validated, rates attached, GSTIN checked against the portal, addresses split so state is a real field rather than a line of free text.
e-Invoice Registration and IRN Handling
The invoice sent to the Invoice Registration Portal, the IRN and signed QR code stored against the record and printed, with cancellation handled inside the window the portal allows.
e-Way Bill Generation and Updates
Bills raised from the same invoice, with transporter, vehicle and distance captured at dispatch, plus Part B updates, vehicle changes, extensions and cancellation where required.
Document Series and Numbering Control
Separate series per branch, document type and financial year, with numbering that cannot skip or repeat, and cancelled documents recorded rather than deleted.
Credit and Debit Note Workflow
Returns, rate differences and post-supply discounts raised as linked documents against the original invoice, with the reason recorded and the stock effect handled at the same time.
Tally and Accounting Integration
Sales, purchases and tax postings written into the right ledgers in your Tally company, with a daily reconciliation report rather than a bulk upload nobody checks.
Purchase and Input Credit Matching
Vendor bills recorded with GSTIN, invoice number and tax split, and compared against the portal data your accountant downloads, so missing credits are chased while the vendor still cares.
Return Preparation Extracts
Data produced in the shape the outward and inward returns need, with exceptions and unmatched items listed separately for your CA to work through.
Rate and Rule Change Updates
When rates, schemas, thresholds or portal specifications change, the configuration is updated and the affected documents identified, rather than discovered by an accountant in filing week.
Where Invoicing Engineering Earns Its Keep
Real-world business processes we configure and automate.
Distributor: Goods Billed in Bengaluru, Delivered to Hosur
A dealer registered in Karnataka takes delivery at a branch across the Tamil Nadu border. The software now takes the ship-to state rather than the billing address, applies IGST, raises the IRN, and creates the e-way bill with the transporter and vehicle captured at the loading bay. The invoices stopped bouncing back from the buyer’s accounts department.
Manufacturer: Job Work Moving Out and Coming Back
Material goes to a subcontractor for plating and returns a week later. Delivery challans are raised for both legs with the correct document type, e-way bills raised where the consignment value crosses the limit, and the stock stays visible as lying with the processor rather than vanishing from the books.
E-Commerce Brand: Returns That Used to Be Handled by Editing the Bill
Staff were changing the original invoice when goods came back. We replaced that with a credit note linked to the invoice and the return reason, the stock movement handled together, and the series left intact. The monthly reconciliation with the marketplace settlement now actually completes.
Service Company: Reverse Charge on Goods Transport
Freight bills from transporters attract reverse charge, and the office was recording them as ordinary expenses. Purchase entry now flags reverse charge at the point of booking, raises the self-invoice where needed, and shows the accountant a clean list each month instead of a hunt through vouchers.
Building Material Supplier: The Truck Held at the Check Post
Invoice raised in billing, e-way bill typed separately on the portal, vehicle number entered with a wrong digit. Now the bill is raised from the invoice record, the driver’s vehicle number is captured on a phone at the gate, and Part B updates when the vehicle changes mid-journey.
Small Retailer: A Case Where Tally Alone Was Enough
A single-counter shop below the e-invoicing limit, billing locally, with an accountant who was managing comfortably in Tally. Building custom invoicing would have added cost and nothing else. We cleaned the item master, fixed the print format and left the rest alone.
Is This Service Right for Your Business?
We partner with established businesses that have outgrown manual processes and want reliable systems.
Businesses Billing Across State Lines
Where place of supply is a real decision on most invoices and getting it wrong means a credit note, a re-issue and an irritated buyer.
Companies Moving Goods Under e-Way Bills
Distributors, manufacturers and suppliers where dispatch involves transporters, vehicle changes and consignments that must not be stopped in transit.
Businesses Crossing the e-Invoicing Threshold
The turnover limit for e-invoicing has come down several times. Businesses that were outside it one year find themselves inside it the next, with software that was never built for it.
Anyone Building or Replacing Billing Software
If a new ERP, portal or e-commerce system will raise invoices, the tax logic should be designed with an accountant at the start rather than patched after the first filing.
Businesses Whose Books Never Reconcile
When the sales register and Tally disagree every month and somebody spends days finding the difference, the problem is usually in how documents are created, not in the accounting.
When You Do Not Need This
A single-counter shop billing locally, below the e-invoicing limit, with an accountant comfortably managing in Tally, does not need custom invoicing engineering. Cleaning the item master and fixing the print format may be the whole job. Equally, if your accounts are genuinely in order and your CA has no complaints, the money is better spent elsewhere. We would rather tell you that after a look at three months of invoices than sell you a project.
Enterprise Capabilities in Plain Business Terms
Place of Supply Determination
Tax split decided from ship-to state, supply type and registration status rather than from the billing address alone.
GSTIN Validation
Checks on the number’s structure and status when a party is created or edited, with the legal name and state pulled back.
HSN and SAC Enforcement
Codes and rates mandatory on item creation, so a product cannot enter the master without the field that the return will need.
Multiple Document Types
Tax invoice, bill of supply, delivery challan, debit note, credit note and self-invoice, each with its own format and rules.
Controlled Numbering Series
Per branch, document type and financial year, without gaps or repeats, and with cancelled numbers recorded rather than reused.
IRN and Signed QR Handling
Registration with the Invoice Registration Portal, the response stored against the invoice, and the QR code printed on the document.
e-Way Bill Integration
Generated from the invoice with transporter and vehicle details, including Part B updates, extensions and cancellation.
Reverse Charge Flagging
Purchases and expenses that attract reverse charge marked at entry, with the self-invoice raised and listed for your accountant.
Rounding and Tolerance Control
A single rounding rule applied consistently across line, tax and invoice totals, which removes the most common source of month-end differences.
Tally Posting With Reconciliation
Entries written to the correct ledgers with a daily comparison report, so a mismatch is found the next morning rather than at filing.
Purchase Register and Credit Matching
Vendor bills captured with the fields needed to compare against portal data and chase missing credits while the vendor still responds.
Exception Reporting
Invoices held, IRNs not obtained, e-way bills expiring, credit notes without a parent and parties with invalid registrations, in one list.
Our Structured 6-Step Delivery Process
A transparent path from your first conversation to a reliable production release.
Review With Your Accountant
We go through three months of your actual invoices and list every transaction type you make. From you we need your CA or accountant for a couple of sessions, and real documents rather than a description of how billing is meant to work.
Rule Book and Document Design
The tax treatment for each transaction type, the document formats and the validation rules written down and signed off. From you we need your accountant’s agreement in writing, because this is the document everything else is built against.
Master Data Cleanup
Item codes, HSN and SAC, rates, party GSTINs and addresses corrected and validated. From you we need somebody who can decide what an unclassified item actually is, since only your team knows the product.
Build and Portal Integration
The invoicing logic built and connected to the e-invoice and e-way bill systems. From you we need portal credentials or the GSP arrangement, and a test environment to work against rather than live billing.
Parallel Billing and Reconciliation
Real invoices raised in both the old and the new way for an agreed period, and the registers compared. From you we need billing staff willing to double-enter briefly, and your accountant to check the comparison rather than assume it.
Go-Live and the First Filing Cycle
The switch, then close support through the first month-end and the first return preparation. From you we need a named contact during filing week, since that is when anything missed will show itself.
What You Receive Upon Project Completion
Everything required to run, maintain, and expand your software without vendor lock-in.
Connects With the Systems You Already Rely On
We build bridges between your software so you don't have to replace functional existing tools.
Government Systems
- Invoice Registration Portal
- NIC e-way bill system
- GST portal data downloads
- GSP and ASP providers
Accounting Software
- Tally Prime and Tally ERP 9
- Zoho Books
- Busy
- Marg
- QuickBooks
Business Systems
- Custom ERP and billing software
- Odoo
- SAP Business One
- Dealer and distributor portals
- Point of sale systems
Commerce and Payments
- Shopify and WooCommerce
- Marketplace settlement files
- Razorpay and Cashfree
- UPI collections
Logistics
- Transporter portals
- Courier aggregator APIs
- Vehicle and driver capture on mobile
- Weighbridge records
Selected for Reliability, Speed, and Longevity
Technology chosen to match your operational scale and long-term maintainability.
Application
Portal Integration
Accounting Bridges
Documents
Reliability
Why Business Owners Choose GullySystem
Your CA Is in the Room From Day One
The rule book is agreed with the person who signs your returns before anything is built. Software that encodes a developer’s understanding of tax is a liability with a login screen.
We Draw the Line at Filing
We engineer the systems that create correct documents and clean data. Filing, positions on the law and representation before the department stay with your chartered accountant, where they belong.
Validation Before the Document Exists
It is far cheaper to stop a save than to issue a credit note. Missing codes, failed registration checks and blank supply positions are caught while the customer is still at the counter.
Reconciliation Built In, Not Bolted On
A daily comparison between billing and Tally means a difference is found the next morning by software, rather than in filing week by a person with a highlighter.
We Plan for the Portal Being Down
The registration portal has bad days. Invoices queue, retry and are tracked, and the billing counter keeps working, because a customer waiting at 6pm cannot be told to come back tomorrow.
Changes Are Watched For
Rates, schemas and thresholds change. We update the configuration and identify the documents affected, rather than leaving your accountant to discover it while preparing a return.
Flexible Engagement Options
Choose an engagement model that matches your operational scope, budget, and timeline.
Invoicing Review
We take your actual invoices, masters and reconciliation differences and report what is wrong, what it costs you and what should be fixed first, with your accountant involved.
e-Invoice and e-Way Bill Integration
IRN registration, QR codes and e-way bills wired into the billing system you already run, with exception handling and retries for portal outages.
Invoicing Built Into a New System
GST logic, document types, numbering, validation and Tally posting designed into an ERP, portal or e-commerce platform as it is built rather than added at the end.
Ongoing Support and Updates
Configuration kept current as rates and specifications change, exceptions reviewed, reconciliation watched, and someone available during month-end and filing week.
Frequently Asked Questions
Straightforward answers to the questions owners ask before getting started.
Do you file our GST returns?
No. Filing, the positions taken on the law, notices and representation before the department stay with your chartered accountant, and we would not want it otherwise. What we do is engineer the systems that feed them: invoices with the right tax and the right fields, IRNs obtained, e-way bills raised, credit notes linked, and extracts in the shape the returns need with exceptions listed separately. Your CA should get clean data and a short list of decisions, rather than a month of reconciliation.
Does e-invoicing apply to our business?
It depends on your aggregate turnover against the limit currently notified, and that limit has been reduced several times since e-invoicing started. Businesses that were comfortably outside it a couple of years ago are inside it now. Your CA will confirm your position, because the calculation involves turnover across registrations and there are categories that are excluded regardless of size. What we can do is make sure the software is ready before you cross, since being unprepared on the first applicable day is the expensive version.
How does e-invoicing actually work?
Your software sends the invoice details to the Invoice Registration Portal, which returns an Invoice Reference Number and a signed QR code. That IRN and QR have to be stored against the invoice and printed on the document. It is not a separate invoice, it is your invoice, registered. Cancellation is possible only inside the window the portal allows, after which a credit note is the route. We wire this so it happens from the same record that prints the bill, rather than as a second data entry job.
What happens when the portal is down?
Your counter keeps working, which is the whole point of designing for it. Invoices are created and queued, the system retries automatically, and a list shows exactly which documents are still waiting for an IRN. Staff can see the state at a glance, and dispatch decisions are made knowingly rather than on the assumption that everything registered. Without this, a portal outage at 6pm means a billing counter full of customers and a member of staff refreshing a browser.
Can the e-way bill be raised from the same screen as the invoice?
Yes, and it should be. The usual failure is that the invoice comes out of the billing software and the e-way bill is typed separately into the portal, which is where the invoice number stops matching and a digit goes wrong in the vehicle number. Raising both from one record removes the re-typing. The vehicle and transporter details can be captured on a phone at the loading bay, and Part B updates when the vehicle changes mid-journey.
Our sales register never matches Tally. Why?
Almost always one of four things, and it is rarely the tax rate. Rounding applied differently at line level and invoice level. Cancelled invoices that were removed from billing but never reversed in Tally. Credit notes posted without a link to the original document. And invoices created in a second place, such as a marketplace or a branch, that never reach the posting job at all. We find which of these it is by comparing a month document by document, then fix the cause and add a daily reconciliation so the next difference is a day old rather than a month old.
Will this work with Tally, or do we have to replace it?
It works with Tally, and most of our clients have no intention of replacing it. Tally stays where the books live and where your accountant works. The invoicing system raises the documents, handles the portal, and posts entries into the right ledgers in your Tally company, with a reconciliation report each day. What we do change is the direction of data: entries should flow from the operational system into Tally automatically, rather than being re-typed by an accounts assistant at day close.
How do you handle branch transfers and job work?
As their own transaction types with their own documents, decided with your accountant rather than assumed. A stock transfer between your own registrations is a supply and needs the right document and an e-way bill where the value crosses the limit. Material sent for job work moves on a delivery challan, comes back on another, and should remain visible in your stock as lying with the processor. Businesses that treat these as ordinary invoices or as nothing at all are the ones with the worst reconciliation problems.
What about reverse charge and export invoices?
Both are configured as distinct transaction types. Reverse charge purchases, such as freight from a goods transport agency, are flagged at the point of entry so the liability is recognised and the self-invoice raised, instead of being found later by an accountant reading vouchers. Exports are raised without tax under a letter of undertaking, or with tax where you are claiming a refund, with the shipping details carried on the document. Your CA decides which applies to your business. We implement both paths.
Can you fix our existing billing software rather than replace it?
Often, yes, and it is usually cheaper. If the software is reasonably built and you have access to it or to its database, we can add tax determination logic, validation, portal integration and Tally posting around what exists. Where it becomes replacement rather than repair is when the source is unavailable, when the data model has no place to record a state or an HSN code, or when the vendor has disappeared and nothing can be changed. We tell you which case you are in after looking, not before.
What drives the cost of this work?
Mainly the number of distinct transaction types you have, and the state of your masters. A business making local sales of one kind is simple. A business doing interstate sales, branch transfers, job work, exports, reverse charge purchases and e-commerce returns has six sets of rules to encode and test. The other drivers are whether the existing software can be modified or has to be replaced, how bad the item and party masters are, whether e-invoicing and e-way bills both need integration, and how much reconciliation history has to be cleaned up before go-live.
What happens when GST rates or rules change?
Rates change, schemas get revised, thresholds move and the portals publish new specifications. Under an ongoing support arrangement we update the configuration, test against the revised specification and produce a list of documents and masters affected, before your accountant meets it in filing week. Without support, a schema change can quietly start rejecting your invoices at the portal. This is the main reason we recommend some continuing arrangement rather than treating the build as finished at go-live.
Can you guarantee our invoices are compliant?
No, and nobody honest will. What we can do is build the software so it applies the treatment your accountant has agreed in writing, refuses to create a document that is missing something the format requires, keeps a trace from each invoice back to the rule that produced it, and reconciles daily against your books. If the department ever questions a document, you can show how it was produced and who approved the rule. The compliance opinion itself is your chartered accountant’s to give, not a software company’s.
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Related Practices & Services
API and System Integration
The connections underneath, between billing, the portals, Tally and the systems that have to agree with each other.
ERP, CRM and Business Software Implementation
When invoicing is one part of a larger system being configured and rolled out across branches.
Data Migration and Moving Off Spreadsheets
Item masters without HSN codes and party masters with invalid registrations, cleaned before they reach a live billing screen.
E-Commerce and Digital Commerce
Online and dealer ordering where the invoice, the tax and the return have to be correct without anyone at a counter.