In this guide 6 sections
Keep a TDL add-on if it only changes a print format and Tally upgrades have not broken it. Rewrite it if the logic is small and someone can read the .tdl file. Move the job beside Tally if it holds approvals, stock rules or customer data. The ledger file stays as it is.
Find out what each add-on really does
Open the TDL folder on the Tally machine and list every .tdl file with its load order. Ask the accountant which screen or printout each one touches. Often nobody remembers. That is normal.
Note the Tally.ini line that loads each file. A file that is listed but never triggered is dead weight. Mark it. Leave it alone for a month.
Then sort the rest by what they touch. A changed invoice layout is cosmetic. An extra mandatory field on a voucher is a rule. A custom report that reads godown stock is a calculation the whole firm may trust.
- File name, size and last modified date
- Voucher type or report it changes
- Fields it adds, hides or makes compulsory
- Which operators see the change daily
- Whether the source is readable or only compiled .tcp
Keep it when the job is cosmetic and stable
A TDL that adds a transport name, a vehicle number or a bank block to a sales invoice is low risk. Back it up and tag it with a version note. Then move on.
The danger is the next Tally Prime release. An add-on that worked on the old Tally ERP 9 screens can fail quietly after an update. Test every add-on on a copy of the company before the live machine is upgraded.
Keep a single page that says what each file does and who may touch it. That page is worth more than the code.
Rewrite it when the logic is small and readable
If the .tdl source is plain text and the rule fits on one screen, a rewrite is sensible. A freelance TDL developer in Surat or Ahmedabad can do it in days.
Give the developer the spec first. Write it as three lines: what the operator enters, what Tally should check, what prints. Ask for the source file, not just the compiled one.
Stop at that point if the rule keeps growing. Each new condition makes the next Tally upgrade harder, and you end up with another file nobody can maintain.
- Spec written before any code
- Source file handed over and stored with the books
- Test on a copy of last year’s company data
- Named owner for the file after delivery
Move the job beside Tally when it carries business rules
Some TDL work is really an application squeezed into a ledger tool. Credit limit checks, dealer price lists, job work challans and approval before a voucher is saved all belong here.
A small system next to Tally can hold those rules and post finished vouchers into Tally through its XML or ODBC interface. Tally keeps the books. The new system keeps the workflow and the approval trail.
This is also the safe route for a Rajkot engineering unit or a Vadodara trader whose add-on reads data that Tally was never built to organise. The ledger file is not rebuilt and the auditor sees the same company.
Pick one add-on and decide this week
Do not review all of them at once. Pick one. Choose the add-on that the most operators touch, or the one that frightens the accountant most when the Tally Prime release notes arrive.
Answer three questions about it. Can anyone read the source? Does it hold a rule or only a layout? Would the books be wrong if it stopped? Your answers point to keep, rewrite or move.
Write the decision on the add-on page and set a date to review it. Then take the next file.
TDL add-on decision sheet
A single sheet listing each .tdl file on its own row. Columns are file name, last modified date, screen or report touched, rule or layout, source readable, who owns it, Tally version tested and decision (keep, rewrite, move). A short box at the foot records the review date and who signed it off.
Open a blank worksheet to printQuestions owners ask
Can we remove a TDL file that nobody uses?
Take a backup of the company and the file first. Rename the file, remove its Tally.ini line and watch for a month. If no operator complains and no report breaks, archive it.
What if we only have the compiled .tcp file?
You cannot read or edit it. Ask the original developer for the source. If that is impossible, record exactly what the screen does and have it rebuilt from that description.
Will a Tally upgrade break our add-ons?
It can. Layout changes between releases move fields and rename objects. Test each add-on on a copy of the data before upgrading the live company.
Does moving a function beside Tally change our books?
No. The ledger stays in Tally and vouchers are still posted there. The other system only holds the workflow, and your accountant and auditor keep working in the same company file.