Custom Tally TDL: How to Brief a Developer Properly

"Can Tally show the vehicle number on the sales invoice?" "Can it block a bill if the customer is over the credit limit?" If you have asked questions like these, you are the person TDL was made for.

TDL, Tally Definition Language, is what lets Tally behave the way your business works instead of the way the default screens assume. The tricky part isn't the code. It is explaining your workflow clearly enough that the developer builds the right thing.

What custom TDL can and can't do

A TDL file loads into Tally Prime or ERP 9 and changes how screens, reports and prints behave. Common requests:

• Extra fields on vouchers, such as transporter name, PO number or approval status.
• Custom reports, say party-wise pending dispatches or a daily cash summary.
• Print formats for invoices, challans and cheques that match your letterhead.
• New menu items that open the report you use ten times a day.
• Simple validations and warnings during entry.

What it can't do is turn Tally into a different product. If you need a full CRM or a mobile app, that is a different project.

Step by step: how a TDL job usually runs

1. You describe the problem in your own words and share a screenshot of where it should appear.
2. We confirm the version. Tally Prime and ERP 9 differ, and so do release numbers.
3. We agree on the exact output: field names, column order, calculations.
4. The code is written and tested on a copy of your data, never directly on your live company.
5. You test with real entries and send corrections.
6. The TDL is installed and loaded, and we show you how to switch it on or off.

What to prepare before you contact a developer

These small things make a surprising difference.

• Your Tally version and whether it's single or multi-user.
• A current backup of the company data. Do this before any customisation.
• A hand-drawn or Excel mock-up of the report or print you want.
• Two or three real examples with the numbers you'd expect to see.
• Any existing TDL files already loaded, as new code can clash with old.

The mock-up is the most useful item. "A report like the ledger, but with a column for last payment date" can be read three ways. A sketch can be read one way.

Mistakes we see again and again

Buying a TDL file from an unknown source

Free or cheap TDLs from random groups sometimes have hidden restrictions or break after an update. Ask for readable source code, or at least know who stands behind it.

Editing the live company first

Always test on a backup copy. A mistaken voucher field can distort reports for months before anyone notices.

Changing the requirement mid-way

Small changes are normal. Rewriting the whole idea after delivery is a new job and priced as such.

Ignoring GST impact

If your customisation touches invoices, check that GST details, HSN and place-of-supply still print correctly. Ask your CA to look at one sample.

What affects cost

Our Custom Tally TDL Code service starts at ₹7,000 with delivery listed at 5 days. A simple new field and print change sits near the lower end. A report that pulls from several ledgers, groups and conditions takes longer. Needing to support both Prime and ERP 9 can add work too. We don't list package tiers for this service, so the final quote follows the scope we agree together.

If you only need a tweak to an existing add-on, that is usually cheaper, and we cover it as a separate service.

Who this is for, and who it isn't

Custom TDL suits businesses whose workflow is stable but doesn't fit Tally's standard screens: traders with challans and transporter details, manufacturers tracking batches, service firms with unusual invoice layouts. If you do the same extra step by hand on every voucher, there's probably a TDL for it.

It isn't ideal if you're still deciding how your business should run, or if you want a complete inventory-and-dispatch system with mobile access. Tally is the wrong place for everything. A good developer will say so and suggest another tool, or an integration, instead of forcing it into TDL.

One more practical point: keep your custom code documented. When your accountant leaves, the next person should know which TDL files are loaded and why.

How we handle this at DegitalService

You send the requirement, we ask follow-up questions (usually a handful), and then you get a clear scope and price before work begins. We test on a copy, hand over the TDL with installation help, and walk you through using it. Revisions on the agreed scope are part of the conversation up front, so you know what is covered.

The details are on the Custom Tally TDL Code page. If your idea is half-formed, message us and we'll help shape it. To start straight away, order here.