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Cutover Fundamentals: Key Definitions and Operational Rules for Go-Live

Learn the key definitions and operational rules that govern the transition from your Legacy System to Light, including Go-Live, Cutoff, migration principles, and posting guidelines for a clean and auditable cutover.

A successful go-live is less about the button you click and more about the clarity of rules you follow. During a system migration, the most common risks—misstated balances, duplicate transactions, and audit gaps—come from blurred lines between the old system and the new one.

This guide establishes those lines clearly.

Below you’ll find the core definitions and operational rules that govern the cutover from your Legacy System to Light. These principles ensure a clean separation between historical activity and future operations, preserve statutory accuracy, and make your first close in Light predictable and low-stress.

Think of this as the rulebook for when data belongs where, how corrections are handled, and why discipline during the transition matters

Key definitions

  • Go-Live Date : The first day you operate in Light. From this date forward, Light becomes your system of record.
  • Cutoff Date : The last day you operate in your Legacy System, end of day. This is the reference point used for your Trial Balance and Open Items and Releases (Open AP / Open AR / Depreciation schedules / Accruals / Prepayments / Deferred revenue)
  • Legacy System : Your previous ERP / accounting software
  • Migration Suspense Account : A temporary balance sheet account used in Light to offset migrated balances (typically Accounts Payable and Accounts Receivable)
  • Rule: after all cutover imports are completed (Open Items + Trial Balance / opening balances), the Suspense Account must net to zero.

Operational rules

To ensure a clean separation between the Legacy period and the Light period, the following rules apply during the transition.

1) Postings / Journals

Before the Cutoff Date :

  • Finalise all transactions in the Legacy System as part of the Month-End Close (MEC) / final close.

From the Go-Live Date :

  • Record all new transactions directly in Light.

Late adjustments (discovered after cutoff but related to the Legacy period)
If you discover a correction after the cutoff that belongs to the Legacy period:

  1. Post it in the Legacy System (to preserve statutory truth for the legacy period).

  2. Mirror it in Light as a journal entry labelled “Prior Period Adjustment”, including the legacy reference (ex journal ID) for audit traceability.

2) Suppliers / Customers invoices

Invoices dated before the Cutoff Date

  • Create and manage them in the Legacy System, those should be migrated to Light as part of the initial upload.

Invoices dated on/after the Go-Live Date

  • Customer invoices and supplier invoices can be processed directly in Light starting the from the first day in the Go-live date Process them in Light (via the AP intake email).

3) Payment & Bank reconciliation

Avoid payments and bank reconciliation in Light until Open AP/AR migration is complete.

Why this matters
You cannot pay or reconcile an invoice in Light if the invoice has not been migrated yet. Waiting ensures:

  • correct open balances

  • clean bank reconciliation

  • fewer exceptions during the first close