Most organisations approach an FRS 102 lease transition as a checklist exercise. Once the opening balances are agreed and the audit sign-off is obtained, the transition is considered done.

In practice, that is not when success is proven. You only find out whether a transition has worked 12–18 months later, when leases start changing, teams move on, and the model must stand on its own under audit scrutiny.

The question, then, is what needs to be designed now so that go-live actually holds up over time.

Whether you are currently in the middle of a transition or preparing for how it will be supported and operated after go-live, below are five mistakes to avoid before they become embedded problems.

Mistake #1: Treating Lease Data as a One-Off Conversion Exercise under FRS 102 

Lease data is often assembled to get through go-live, not to operate afterwards. Embedded leases and renewals are missed, complex arrangements are parked, and responsibility is spread across teams and spreadsheets. There is no clear mechanism to identify new leases or validate the population once transition activity winds down. It works on day one, but it rarely holds over time.

How to avoid it

• Decide who owns the lease population before go-live, and make it explicit
• Load all leases into a single source of record, not working files
• Build lease identification into contract intake so new agreements are reviewed by finance as they arise
• Schedule a defined completeness review post go-live, rather than waiting for audit requests 

Mistake #2: Flexibility Without Judgement Governance in FRS 102 Lease Accounting

FRS 102 allows judgement, but that flexibility is often applied inconsistently. Similar leases end up being assessed differently by different people. Assumptions about lease terms, discount rates, and exemptions shift from one period to the next. With no agreed starting point, routine questions keep escalating just to get a consistent answer. Over time, senior staff become bottlenecks, and outcomes depend more on who is asked than on what was originally agreed.

How to avoid it

• Decide upfront which judgements must be applied consistently across the portfolio
• Document those positions once and treat them as the default, not guidance
• Define which decisions require senior input and which do not
• Record judgement rationale as decisions are made, not reconstructed for audit

Mistake #3: Forcing Legacy Tools to Support FRS 102 Lease Accounting 

Tools that worked before FRS 102 are often pushed far beyond what they were designed to handle. Lease data lives in spreadsheets with heavy reliance on individual owners. Version control is fragile. Audit trails are partial or reconstructed after the fact. As leases change, manual workarounds multiply, and small fixes compound into a process that is difficult to scale or rely on. What starts as manageable at transition becomes increasingly brittle as portfolios grow and activity increases.

How to avoid it

• Be clear, during transition, about what the lease model needs to support after go-live, including modifications, reassessments, and audit evidence
• Reduce reliance on individual files and key people for critical calculations and updates
• Ensure lease changes can be tracked end-to-end without manual reconstruction
• Where legacy tools cannot support this at scale, assess whether the operating model itself needs to change 

Mistake #4: Reactive Lease Lifecycle Management under FRS 102

Lease changes are often treated as exceptions rather than routine activity. Commercial teams agree on extensions, rent changes, or break decisions without finance involvement, and the accounting impact is picked up late, if at all. Reassessment triggers are missed or applied inconsistently, and changes surface at period end through catch-up entries and reporting delays. Where systems or processes make lease changes hard to capture, teams fall back on manual fixes or external support, driving cost and operational friction over time.

How to avoid it

• Design lease processes on the assumption that changes will happen, not as exceptions
• Link commercial lease decisions to finance review so accounting is assessed when changes are agreed
• Define reassessment triggers clearly and apply them consistently
• Ensure lease changes can be processed without manual workarounds or external intervention

Mistake #5: Designing for Minimum Compliance Instead of Audit Resilience under FRS 102

Some transitions are designed to meet the letter of FRS 102, but not to withstand audit scrutiny over time. Documentation is thin, evidence trails are fragmented, and controls work only as long as the same people and lease population remain in place. There is little visibility over what lease changes have occurred, when they were assessed, and how they affected the numbers. It holds together at go-live, but begins to fail as teams change, portfolios evolve, and auditors start asking questions beyond basic compliance.

How to avoid it

• Design documentation and evidence trail as part of the transition, not as an audit afterthought
• Assume staff turnover and portfolio change, and build processes that do not rely on individual memory
• Test controls against audit scrutiny, not just management sign-off
• Ensure lease lifecycle events and their accounting impact are visible and easy to retrieve

What Actually Makes an FRS 102 Lease Accounting Transition Work

Design your FRS 102 lease accounting transition as an operating model, not a compliance project. That means planning for lease changes, governed judgement, staff turnover, audit scrutiny, and growth from day one.

If your transition can absorb those pressures without constant rework, it will hold. If it cannot, the issues will surface later, regardless of how clean the go-live looked.

That is the difference between an FRS 102 lease accounting transition that merely complies and one that lasts.