When Is the Last Safe Date to Start Your NAV Upgrade Before January 2028?

Microsoft Dynamics NAV extended support ends on 11 January 2028. That date is fixed, and most businesses running NAV know it is coming. What is less well understood is what the deadline means in practice, because the critical question is not when support ends but whether you have left yourself enough time to be live on Business Central before it does.

BC4's typical NAV to Business Central project, for a business of real operational complexity, runs between 18 and 24 months. That range is not conservative padding. It reflects the work of migrating data, converting or replacing customisations, rebuilding integrations, running user acceptance testing, and managing the change across a live business. Simple NAV environments with limited bespoke development can move faster. Retail operations with multi-site POS systems, loyalty integrations, and eCommerce connectors, or sports organisations with ticketing interfaces and multi-entity finance structures, are at the 24-month end of that range, sometimes beyond it.

The arithmetic that follows from those two facts is not complicated, but very few businesses have actually worked through it. This post does that calculation explicitly and explains what it means depending on the complexity of your environment.

What January 2028 actually means for NAV users

When Microsoft ends extended support, it stops releasing security patches for the product. NAV will not switch off on 12 January 2028. Your system will continue to function. But you will be running ERP software with unpatched security vulnerabilities, no vendor bug fixes, and no access to regulatory updates.

For UK businesses, that last point carries specific weight. HMRC compliance requirements evolve. Making Tax Digital continues to expand in scope. VAT reporting obligations change. Microsoft will not update an unsupported product to accommodate any of those changes. Businesses processing payments, holding customer data, or operating under audit requirements face compounding risk the longer they remain past the deadline.

This is not a reason to panic. It is a reason to plan with a clear, honest timeline in hand, which is what the rest of this post provides.

Working backwards from the deadline

The calculation starts with the end date: 11 January 2028. Working backwards using BC4's project duration:

18 months before January 2028 is July 2026. 24 months before January 2028 is January 2026.

If you are reading this in mid-2026, the implication is direct. A project requiring 18 months needs to start by approximately July 2026 to land a January 2028 go-live. A project requiring 24 months should have started in January 2026 to hit that same target. Both of those calculations assume the project starts in earnest immediately. The assessment, scoping, and commercial agreement phase typically adds six to eight weeks before implementation formally begins, and that time has to come from somewhere.

The practical conclusion for any organisation starting its planning now is this. A well-managed go-live before January 2028 is still achievable, but the margin is narrow. A project that begins in Q3 2026 can realistically target a go-live in Q4 2027, providing a short buffer before the deadline. A project that starts in Q4 2026 or later is targeting a January 2028 go-live with no buffer at all. And that assumes nothing goes wrong along the way, which in any project of this scale is an optimistic assumption.

Why retail and sports environments need more time

BC4 works with retailers, sports clubs, and major event operators. These organisations are consistently at the complex end of the NAV upgrade spectrum, and that complexity is structural rather than incidental.

A multi-site retailer typically runs NAV alongside LS Retail, bespoke POS configurations, loyalty scheme integrations, eCommerce connectors, and stock management rules that have accumulated over years of trading. A sports club adds matchday retail operations, fan loyalty programmes, ticketing interfaces, merchandise management across physical and digital channels, and often multi-entity finance structures. These are not clean NAV environments. They are heavily layered systems where the scoping phase regularly surfaces complexity that generic timelines do not account for.

For organisations in these sectors, 24 months is not a worst case. It is a realistic baseline, and some projects take longer. The honest advice for a retail or sports operator reading this in mid-2026 is that a managed go-live before January 2028 is achievable, but only if the decision to start is made now.

There is also the question of go-live timing within the trading calendar. Multi-site retailers will not accept a go-live in November or December. Sports clubs will not accept a go-live mid-season. These constraints reduce the number of viable go-live windows significantly and have to be factored in from the very start of the project, not retrofitted once implementation is underway.

The partner capacity problem nobody is talking about

There is a second constraint that most businesses do not factor into their planning: partner capacity. Experienced Business Central implementation partners have finite delivery resources. As January 2028 draws closer, those resources will progressively be committed to organisations that have already started their projects.

This is not theoretical. The dynamic is already visible in the market. Partners with genuine retail and sports ERP experience are a small group. Organisations that delay their assessment into late 2026 or 2027 may find that their preferred partner does not have capacity for a project starting at that point, or that the partners with available capacity do not have the vertical expertise their project requires.

Starting a conversation with an implementation partner now does not mean committing to a full implementation immediately. It means having a scoping conversation, getting an honest project estimate for your specific environment, and reserving capacity in the delivery pipeline. That conversation costs nothing and buys significant flexibility later in the process.

What to do if the timeline is already tight

If the calculation above has confirmed that your timeline is tighter than comfortable, there are practical steps worth taking immediately.

Get a proper scoping assessment. Generic timelines are ranges. Your project has a specific number based on your actual NAV environment: the number and complexity of customisations, the state of your data, the integrations that need to be rebuilt, and your go-live constraints. A scoping assessment from an experienced partner gives you that number, and without it you are planning in the dark.

Be honest about what you are actually running. Retail and sports organisations often underestimate the scope of their NAV customisations because the system has been stable for years. Stable does not mean simple. A system that has run without incident for a decade may still carry extensive bespoke development that needs to be addressed before migration. Better to know now than six months into a project.

Consider a phased approach. For organisations where a full upgrade before January 2028 is genuinely not achievable, a phased approach is worth exploring. Core finance processes can often move onto Business Central in an initial phase, with retail, POS, and operational modules following in a second phase. This reduces the risk of running past the support deadline while managing the scope of the initial project. BC4 can assess whether a phased approach makes sense for your specific environment.

Frequently Asked Questions

Does NAV stop working after January 2028?

No. NAV will continue to function after Microsoft ends extended support on 11 January 2028. What stops is the release of security patches, regulatory updates, and bug fixes. Running unsupported software carries growing risk over time, particularly for UK businesses subject to HMRC compliance requirements or operating under audit obligations.

How long does a NAV to Business Central upgrade take?

BC4's typical project runs between 18 and 24 months for organisations of meaningful operational complexity. Simpler NAV environments with limited bespoke development can move faster. Retail and sports operations with POS systems, multi-site stock, loyalty integrations, and ticketing interfaces are generally at the 24-month end of the range. A scoping assessment of your specific environment is the only reliable way to estimate your project duration.

What is the last date I can start my NAV upgrade and still go live before January 2028?

Working backwards from 11 January 2028, an 18-month project needs to start by approximately July 2026 to hit the deadline. A 24-month project should have started in January 2026. For organisations starting in mid-2026, a Q4 2027 go-live is achievable but requires committing without delay. For complex retail or sports environments, the margin is slim and a late start leaves no room for the complications that are inevitable in a project of this scale.

Can I stay on NAV after January 2028?

Technically yes. Practically, the risk grows as unpatched security vulnerabilities accumulate and Microsoft makes no further regulatory updates to the product. Most organisations find that the cost and compliance exposure of remaining on unsupported NAV eventually exceeds the cost of moving, and by that point the project will be more expensive and partner capacity more constrained than it is today.

What if my full upgrade cannot be completed before January 2028?

A phased approach is worth exploring. Core finance processes can often move to Business Central in an initial phase, with retail, POS, and operational modules following in a second phase. This reduces the risk of running past the support deadline while containing the scope of the initial project. BC4 can assess whether a phased approach makes sense for your environment and trading calendar.