Migration & implementationJuly 10, 2026 10 min read

Phased Migration from 1C and BAS: How to Switch Without Stopping Your Business

Short answer: from our experience and the experience of our clients, migrating from a system that has been running for years is a highly non-trivial task that takes time and careful planning. At VlasnaCRM we developed a process that makes migration from 1C and BAS phased: the old system and the new CRM run in parallel for a while, processes are moved in blocks with data reconciliation, and the business keeps running smoothly with zero downtime the whole time.

0
days of business downtime during phased migration
2-3 weeks
to launch the first working block
1-4 mo
full migration depending on volume
100%
of data reconciled at each stage

Why migrating from 1C/BAS is non-trivial

A system a business has run for years is not just a piece of software. It is dozens of configured processes, a history of data, team habits and a multitude of small customizations that often only a few employees remember. That is exactly why trying to move everything in one big leap almost always ends in stress, errors and downtime.

From our experience and the experience of our clients, the main challenges of migration are:

Years of accumulated processes

Complex logic

Over years of working in 1C/BAS you accumulate dozens of interconnected processes, customizations and exceptions. Migrating everything at once is a huge risk.

Large volume of data

History and balances

Customer base, deal history, stock balances, documents from many years. The data must be migrated carefully, with reconciliation and no losses.

Team habits

Human factor

Employees have worked in a familiar interface for years. An abrupt change causes resistance and mistakes if the team is not given time to adapt.

Business continuity

Operations can't stop

Sales, shipments and accounting can't be paused. Any downtime means lost money and unhappy customers.

Our approach: phased migration

At VlasnaCRM we developed a process that turns a painful “move” into a manageable sequence of small steps. Instead of stopping the business and migrating everything at once, we break the migration into independent blocks and launch them gradually.

The core idea is simple: the business should not feel the migration. While the new CRM gradually takes over processes, the old system keeps running - so sales, inventory and accounting never stop for a single day.

The migration process step by step

1

Audit and process map

3-7 days

We dive into your business: how you work in 1C/BAS, which processes are critical, what data and integrations are involved. We build a migration map with priority blocks.

2

Phased migration plan

3-5 days

We split the migration into independent blocks (e.g. customers → sales → inventory → finance). For each block we define the order, the data and the readiness criteria.

3

Pilot block in production

2-3 weeks

We launch the first process in the new CRM in parallel with the old system. The team tries it on real tasks, we collect feedback and fine-tune.

4

Parallel work and expansion

from 3 weeks

1C/BAS and the new CRM run at the same time. We gradually migrate the next blocks, reconciling data at every step - the business stays operational the whole time.

5

Final reconciliation and 1C/BAS shutdown

3-5 days

Once all processes run in the new system and data is reconciled, we safely decommission the old system. You are fully independent of 1C/BAS.

The principle of parallel operation

The key to a zero-downtime migration is the parallel operation of the two systems. Here is what it gives your business:

  • The old 1C/BAS stays operational while the new CRM gradually takes over processes
  • The team learns the new system on real tasks without rushing
  • Data is reconciled at every step - you can see that nothing is lost
  • At any stage you can roll back to the old system with no risk
  • We shut down the old system only when everything new works flawlessly

Phased vs one-time

CriterionOne-timePhased
Business downtime during migrationYes
Risk of data lossHighMinimal
Time for the team to adaptNone
Ability to roll back to 1C/BAS
Parallel operation of two systems
Data reconciliation at each stage
Control of results at every step
Stress and load on the teamMaximumModerate

Planning a migration from 1C or BAS?

We'll build a phased migration plan tailored to your business, move your data and launch a custom CRM - with no downtime and no risk of losing data.

Frequently asked questions

Can you migrate from 1C or BAS without stopping the business?
Yes. The phased approach means the old system (1C/BAS) and the new CRM run in parallel for a while. We migrate processes in blocks, so the business keeps running with zero downtime.
How long does a phased migration from 1C/BAS take?
Depending on the volume of data and number of processes, a phased migration usually takes from 1 to 4 months. The first working block can go live in as little as 2-3 weeks.
What happens to the old data from 1C and BAS?
We migrate the customer base, deal history, stock balances and documents. Historical data is preserved, and reconciliation at each stage guarantees that nothing is lost.
Why is a phased migration better than a one-time switch?
A one-time switch (“big bang”) stops operations and carries a high risk of errors. A phased approach reduces risk, gives the team time to adapt, and lets you roll back to the old system at any step.

Key takeaways

  • Migrating from a system that has run for years is a complex task that takes time
  • A one-time migration carries a high risk of downtime and data loss
  • The VlasnaCRM phased process moves processes in blocks without stopping the business
  • The old and new systems run in parallel, with data reconciled at every step
  • The first working block goes live in as little as 2-3 weeks
  • We shut down the old 1C/BAS only after full reconciliation of all processes