Custom TDL Add-on for TallyPrime

@Heorhii01

Hi, I hope you're doing well. I understand you're looking for a custom TDL add-on for TallyPrime 7.1 that extends stock item pricing with multiple successive discounts while keeping invoice calculations accurate, editable, and fully compatible with existing Tally workflows. The goal is to enhance sales invoicing without affecting standard accounting, GST, stock valuation, or reporting functionality. I will develop a source-based TDL solution using proper persistent UDFs for stock items and vouchers, adding item-level selling price and three configurable discount fields with automatic retrieval during invoice creation. I will implement successive discount calculations, editable invoice-level values, support for invoice alteration/duplication/printing/export, and ensure compatibility with GST invoices, different units, price levels, and relevant voucher types. I will also provide the editable TDL source, installation guide, backup procedure, and testing support. My focus is on delivering a reliable TallyPrime extension with accurate calculations, clean implementation, future maintainability, and a smooth handover process for long-term use. Best regards, Heorhii

@rajeshrolen

Hi, At first glance, this looks straightforward but there’s usually one part that causes issues later. I’ve handled similar work before and can help you avoid that. Regards, Rajesh

@aakaashberi

The decision that matters here is where the three discount values live at invoice time. The obvious build adds UDFs to the Stock Item and reads them live when the item is picked. That passes a demo and quietly corrupts history: since you also want the columns while viewing and duplicating an invoice, an old voucher would re-read today's master values and re-price itself. Change a discount next month and last month's invoices change with it. So the discounts are stored twice, deliberately: as UDFs on the Stock Item master (the default), and snapshotted onto the inventory entry line of the voucher at save. The master only supplies defaults on fresh entry. Viewing or duplicating then shows what was actually billed. Second, rounding, because your example is exact: 1000 to 900 to 855 to 837.90. I round Net Rate to 2 decimals and derive Amount as Net Rate x Qty, so the printed rate and the line total always tie. If you would rather hold full precision internally and round only Amount, tell me before I start - it is a one-line difference and a large reconciliation difference. Source-based TDL for TallyPrime 7.1, columns in your stated order, working on create, alter, duplicate and view. 2 days, source code included.

@henrlih

I completely understand your objective of creating a flexible TDL add-on where stock item pricing and three independent successive discounts are automatically managed throughout the TallyPrime workflow. Your concept is really great because it solves a common business problem of maintaining accurate product pricing and invoice-level discount control. I can implement this functionality with a reliable TDL architecture that supports item creation, invoice editing, voucher saving, PDF/export printing, and future TallyPrime 7.x compatibility. I would like to know if manually modified discounts inside an invoice should remain unique only for that invoice without affecting the item master values.

@sameerr153

Hello, I have reviewed your TallyPrime 7.1 requirement. We already have a ready-to-use Windows-based Inventory Management and Billing Software solution, and we can customize it according to your business workflow. We can also integrate the solution with TallyPrime using available integration methods such as XML/ODBC, allowing synchronization of inventory, sales, purchases, ledgers, GST-related data, and accounting transactions. For your specific requirement of item-wise pricing and three-level discount calculation, we can implement the required logic either through Tally integration or through a customized TDL add-on depending on your preferred workflow. The advantage of this approach is that you get a complete business solution with inventory, billing, reporting, and accounting connectivity instead of only a TDL modification. Estimated timeline: 3–5 weeks depending on final scope and Tally workflow requirements. I would like to understand your current Tally setup and whether you need the functionality inside Tally screens only or you are open to an integrated billing and inventory solution. Looking forward to discussing this further.