How Should Your Business Roll Out ERP – Big Bang, Parallel or Phased?

Are you planning to implement a new ERP system? One of the first things to think about is how to onboard the new software. But with several ERP implementation methods available, each with its benefits and pitfalls, how do you decide on the one that’s right for your business?

In this guide, we’ll be looking at three of the main types of ERP implementation, including big bang, parallel and phased, talking you through how they work and the pros and cons to be aware of. Choose the method you’re interested in from the links below or read on for the complete guide.

Big Bang


What is Big Bang ERP Implementation?

The big bang ERP implementation method is simple: it means everyone within your business starts using the new ERP system at the same time. Sound daunting? Remember, lots of preparation will have already taken place, so things should, in theory at least, go smoothly.

With the big bang method, you’re effectively picking up the entire business and moving it to a new system on the same day. This might sound like a logistical nightmare, and one which could result in a whole array of issues, but you and your ERP vendor will have spent months preparing for the go-live date – transferring data, testing processes, and making sure your staff are ready to take the reins of the new system.

One of the most crucial things to get right with the big bang method is change management. Transferring the entire business to a new system places huge demands on your staff, so adequate preparation is needed to mitigate change risk factors and ensure everyone is ready for the big switch.


colleagues discussing work

What are the Pros and Cons?

As with all ERP implementation strategies, the big bang method has its benefits and pitfalls. Here, we’ll take a look at the pros and cons to be mindful of when choosing this type of rollout.



  • Short implementation time – big bang has the shortest rollout time of any implementation model. With all modules going live at the same time, it takes a fraction of the time to migrate to the new system compared to other implementation methods.
  • Immediate ROI – consider the cost of running two systems concurrently, as is the case with other rollout models; it can feel like money wasted. The nature of big bang means only ever using one system at a time, keeping costs to a minimum. Plus, the immediacy means your staff can begin extracting value from the new system right away, bolstering short-term ROI.
  • A clear, attractive strategy – because big bang has a single deadline day, your business has a date to work towards, and this is beneficial for two reasons. First, it guarantees buy-in from senior stakeholders, with a discernible endpoint making the project more tangible. And second, it prepares your staff and keeps them in the loop, so the whole business is aware of the strategy and what’s expected when.



  • Staff readiness – how well your employees take to the new system can make or break the success of a big bang rollout. And even with sufficient training, there’s no guarantee that personnel will grasp things right away. The big bang approach is, therefore, only effective when members of staff are fully up-to-speed ahead of the go-live date.
  • Drop in productivity – a side effect of inadequate training and preparation is a drop in productivity. If your system is riddled with issues and employees are struggling to use it, this can have huge implications for the system’s effectiveness.
  • A need for real-time, real-world and on-the-fly testing and fixes – with the old system offline and the business reliant on new technology, IT teams must be ready to assist with bug fixes and repairs on the fly. Any downtimes can be of significant detriment, and with no fall back in place, any glitches need to be dealt with swiftly to guarantee the efficacy of the new system.


programmer looking at code




What is Parallel ERP Implementation?

As the name suggests, parallel implementation involves running both systems concurrently until the business is ready to make the switch from old to new. This is very much the shallow-end-of-the-pool when it comes to deploying ERP technology, a far cry from big bang’s leap-of-faith approach.

The parallel ERP method is designed to give businesses a safety net when transitioning from one system to another. This does, of course, come at a cost, but for new adopters or those wary of rapid change, it can be the hand-holding needed to secure buy-in and ensure optimum continuity.


What are the Pros and Cons?



  • A welcome safety net – unlike big bang, the go-live date for a parallel ERP implementation passes with little fanfare and minimum risk. With the old system still in use, businesses have a fallback option, and it’s likely that the new software won’t take over from the new until everything is ready.
  • Real-world training aid – one of the biggest reasons to go for parallel implementation is for the robust training provision it affords staff. The fact that the old system is still up and running provides the freedom to trial and adapt to the new software before it’s fully adopted, so employees can see how it fits around their day-to-day duties.
  • Iron out the flaws ahead of full adoption – parallel implementation allows for the most comprehensive testing and bug fixing, meaning minimal downtimes when the transition period ends. This reduces demand on IT teams, too, allowing for a careful, methodical approach to onboarding the new tech.



  • Expensive – parallel ERP implementation is by far the most expensive option, chiefly because it means running two systems at the same time. This may make it more difficult to ensure stakeholder buy-in or could lead to cash flow issues, not to mention delay the point at which the new system starts delivering value and ROI.
  • Errors and frustration – the nature of parallel ERP deployment often requires data entry across both systems, which can be frustrating and time-consuming for staff. Not only that, but errors and confusion can easily creep in, meaning robust processes must be in place to forego such issues.
  • Lack of clarity can cause weariness and confusion – the parallel approach raises questions about timeframes, resource management and progress; when will senior stakeholders see the positive change brought by the new system? With both systems in place, there can be a lag between the go-live and transition, a period of inertia that may be frustrating for those who previously expressed doubts about the technology.


colleagues discussing work




What is Phased ERP Implementation?

The phased ERP implementation model takes elements from both big bang and parallel, allowing for businesses to transition from one system to another in line with a predefined process. For this reason, it’s among the most attractive and popular rollout models, offering the reassurance of not having the old system pulled out from under you, whilst at the same time ensuring tangible, discernible progress.

With a phased deployment approach, businesses roadmap the implementation module by module, usually within a two-to-four-week window. This allows for a methodical, drip-fed transition from old to new, which can benefit both day-to-day personnel and IT teams charged with overseeing the rollout in a measured, systematic way.


What are the Pros and Cons?



  • Reduced risk – as with parallel, phased adoption keeps operational risk to a minimum. With a staged transition in place, different parts of the old system can be switched off only when personnel are content with the new, providing a safety net without hindering progress.
  • Safeguards productivity – the module-by-module approach is excellent at conserving productivity, with staff better able to adapt to individual parts of the new system without feeling overwhelmed. This reduces downtime and the likelihood of errors, making for an efficient and timely onboarding process.
  • Manageable fixes and maintenance – arguably the best thing about phased ERP adoption is the ease at which the rollout can be managed by IT personnel. With methodical steps in place, IT teams can focus on single modules at a time, which can be of huge benefit in ensuring accuracy and precision throughout the system.



  • Interconnection between new and old systems can be expensive – the modular interconnection between two systems can be expensive and complex, raising the overall cost of the project. However, it’s still not as resource-intensive as the parallel approach.
  • Long implementation time – rollout time can creep up for a phased implementation, particularly if you encounter more issues than you’d accounted for. This can cause tension with senior stakeholders keen to start seeing value from the new system, as well as confusion and frustration from day-to-day users.
  • Modular disruption can result in change fatigue – change management is critical in the case of phased implementation. With different modules and processes changing day after day, this can put a lot of strain on staff, who may feel fatigued by the many changes happening around them. Stay mindful of this, and make sure the right processes are in place to support the transition.


So there you have it, a complete guide to the big bang, parallel and phased ERP implementation models, and the pros and cons they present. If you need help choosing the right ERP deployment model for your business, JS3 Global can help. Our experts can guide you towards the right products, solutions and implementation method for your needs. For more information or to speak to a member of our team, visit the homepage or call us on +44(0)161 503 0866.