ERP implementation in 90 days: a phased rollout plan

The two weeks before the rollout starts decide most of what follows.

• A written scope per phase. Which modules, which reports, which integrations, and what "working" means for each.
• One owner per process. Not the IT person. The sales manager owns sales, the store in-charge owns stock, the accountant owns GST. They make decisions and sign off.
• A data inventory. Where every master and balance lives today: Tally companies, Excel files, a CRM, someone's notebook. Read our data migration checklist before this step.
• Cut-over dates. Each phase goes live on the first day of a month, so GST returns and payroll are not split between two systems.
• A decision on what stays. Many businesses keep Tally for final accounts for the first year and post summarised entries from the ERP.

This phase replaces the counter or the billing desk.

• Load the item master with HSN codes and current GST rates. Since 22 September 2025, most goods fall in the 5% and 18% slabs, so check every item against the new rates rather than copying old ones.
• Load parties with GSTIN, state and credit terms, and price lists.
• Set up users, roles and invoice formats.
• Train billing staff on real invoices in a test copy, not on a slideshow.
• Go live on the first of the month and run the old system alongside for one to two weeks.

Exit criteria: each day's sales totals, tax totals and party-wise invoices match between old and new for a full week, and billing staff no longer ask for help on routine bills.

Now the ERP takes over what comes in and what sits in the godown.

• Purchase orders, goods receipt and purchase bills.
• A physical stock count on the cut-over date, entered as opening stock per godown.
• Godown-to-godown transfers. A Noida distributor with three godowns should see stock by location and move it with proper transfer documents.
• Integrations: e-invoicing through a GSP, e-way bills, payment gateway or bank statement import. Our guide to GST e-invoicing in an ERP explains what to test.

Exit criteria: stock quantity per item per godown matches a spot physical count within an agreed tolerance, purchase bills reconcile with supplier statements, and e-invoices and e-way bills generate from the ERP without manual portal work.

Do not cut over payroll in the middle of a month, and do not file your first GST return from the new system without a parallel check. Both are easy to get wrong and expensive to correct. If a phase slips, move its go-live to the next first-of-month rather than squeezing it.

This phase depends most on the business. A 120-person Pune manufacturer would focus on:

• Bills of material and production orders, with material issued against each order.
• Finished-goods entry and costing.
• Attendance and payroll, run in parallel with the old method for one full cycle. Statutory deductions need particular care; our guide to PF, ESI, PT, TDS and LWF in payroll covers what to check.
• MIS reports and the owner's dashboard, built from what the owner actually reads today.

A trading business might use these weeks for a CRM, a salesperson app, or dealer schemes instead.

Exit criteria: one payroll cycle matches to the rupee for every employee, production costs reconcile with stock movements, and the owner signs off that the reports answer his daily questions.

• The decision-maker, usually the owner or a director, for 30 minutes a week to settle questions nobody else can.
• Process owners, about two to four hours a week each, more during their phase's go-live.
• A super-user per department, who learns the system first and becomes the first line of help for colleagues.
• The implementation partner's project lead, who keeps a written list of open issues, owners and dates.

A weekly 30-minute review using that list keeps everything visible. If the same item is open three weeks in a row, it needs the decision-maker, not another reminder.

• Dirty data. Duplicate items and parties slow every phase. Clean before loading, not after.
• Late decisions. A pricing rule nobody can agree on holds up the whole sales phase.
• New features mid-rollout. Keep a "phase four" list and park every new request there. Most will look less urgent after go-live.
• Third-party onboarding. GSP accounts, payment gateway approvals and biometric device integrations depend on other companies' timelines. Start those in week one.
• More than one company or GSTIN. Each adds setup and testing. Pilot one entity or one branch first, then extend.

• The old system is read-only, kept for reference only.
• A full month-end close has happened in the new system.
• GST returns for a full period have been prepared from the new system.
• Every user has logged in during the last week, and support requests are falling.
• A backup has been restored successfully on a test server.

After that, plan 30 days of close support while people settle in.

Train each group just before its own phase goes live, not everyone in week one. Billing staff trained in week one and asked to use stock screens in week seven will have forgotten most of it.

Keep sessions short and practical: 45 minutes on the screens that person will use, with their own items and customers loaded in a test copy. Record the session on a phone so new joiners can watch it later. Give each department a one-page cheat sheet with the five tasks they do most often.

Then train again two to three weeks after go-live. That second round is where the real questions come out, because people have now hit the cases the first session skipped: a sales return, a partial dispatch, an invoice raised to the wrong branch. Super-users should collect those questions during the weeks in between, so the session answers them directly.

ERPSetu, our multi-industry ERP, turns modules on by business type, so a salon never sees production planning and a manufacturer never sees appointment booking. The same principle helps a rollout: switch modules on phase by phase, so users only see what has been prepared for them. You can read how it is built in the ERPSetu case study.

Can an ERP go live in the middle of the financial year?

Yes. Start on the first day of a month, bring in opening balances as on that date, and keep earlier months in the old system for reference and returns.

Should we keep Tally running in parallel?

For a defined period, yes: one to two weeks per phase for operations, and often a full year for final accounts if your CA prefers it.

Can we pilot one branch first?

Yes, and for multi-branch businesses it is usually the safer route. Fix problems in one branch, then roll out the rest in quick succession.

What if a phase slips?

Move its go-live to the next first-of-month. A two-week delay costs less than a messy cut-over.

How much of our staff's time will this take?

Expect the people who own each process to spend a few hours a week throughout, and noticeably more during their own phase's go-live week.

Write your phase plan on one page: what goes live in each phase, who owns it, and the date. If you want a partner to run it with you, see our ERP development service.