A spreadsheet can get a business through its first FRS 102 Section 20 close. It is much less reliable at getting a business through the second, third, and fourth. Leases get modified, rent reviews land, an auditor asks for the history behind a figure rather than just the figure itself, and the model built for the transition date starts to show its limits. For most UK and Irish finance teams the practical question isn't whether to eventually move to dedicated software; it's recognising the point at which the spreadsheet has already become the bigger risk.
Those signs are recognisable once you know what to look for, and LOIS has watched what tends to happen to spreadsheet-based lease models once the standard settles in. This piece works through both: the signs themselves, and the six steps a spreadsheet-to-software migration actually goes through. See FRS 102 lease accounting for an overview of what the standard requires and how LOIS supports it.
Before the FRS 102 Section 20 changes, most leases sat off the balance sheet and a spreadsheet only needed to track a rental charge. Under the revised standard, effective for accounting periods beginning on or after 1 January 2026, most leases are recognised as a right-of-use asset and a corresponding lease liability, with depreciation and interest replacing the old rental line. That is a heavier calculation on its own, but it is not the part that breaks spreadsheets over time. What breaks them is that the position is never final: every rent review, extension, scope change, or early termination triggers a remeasurement, and FRS 102 expects that remeasurement to be documented, consistent, and traceable back to the original lease. For the full picture of what changed and why, see FRS 102: what UK and Irish businesses need to know about the new standard, and for how the standard compares to IFRS 16, FRS 102 vs IFRS 16: key differences finance teams need to know.
None of these signs on their own is a reason to panic. Together, they describe a portfolio that has outgrown the tool tracking it.
A business with a handful of stable leases and no growth on the horizon can reasonably stay on a well-built spreadsheet for now. Most organisations transitioning to FRS 102 for the first time, with property, fleet, or equipment leases across more than one site, do not fit that description.
LOIS worked with firms such as Mazars and their clients as IFRS 16 moved out of training rooms and into live reporting, and the pattern that emerged there is the same one FRS 102 preparers are now walking into. The greatest pressure did not come from a lack of technical understanding of the standard. Finance teams generally understood right-of-use assets, lease liabilities, and discount rates well enough to get an opening position onto the balance sheet. The pressure came later, once systems and processes that had been designed to produce one set of transition numbers were asked to keep producing correct numbers indefinitely, through modifications, reassessments, and portfolio growth that training day scenarios never covered.
Auditors changed how they tested lease accounting during that period too. Scrutiny moved away from whether a number was correct in isolation and toward how the number was produced: how a decision was made, how a change was tracked, and whether the same standard of evidence was applied consistently across every reporting period. A spreadsheet built under time pressure to hit a transition date rarely holds up well against that kind of question a year later, because version control, access rights, and audit trail all sit outside the tool rather than inside it. Several transition risks compound quietly as a result: knowledge concentrates in whoever built the model rather than in the process itself, the reasoning behind an old judgement gets harder to reconstruct the further it recedes, and changes made in a hurry during a busy close carry a higher chance of error that surfaces months later, not on the day it happens.
FRS 102 gives preparers the chance to apply that lesson before it costs them anything, rather than after.
The gap between a spreadsheet and a purpose-built platform is narrowest at the transition date and widest a year later, once modifications have accumulated. The table below focuses on the areas where that gap does the most damage under sustained FRS 102 reporting.
| What matters after transition | Spreadsheet | LOIS |
|---|---|---|
| Processing a modification | A new calculation is built into the existing model by hand, with no independent check that the formula was carried through correctly | The remeasurement is calculated within the platform against the lease's existing terms, and the prior position is preserved rather than overwritten |
| Audit trail | History depends on file naming, saved versions, and whoever remembers why a cell was changed | Every lease event and modification is timestamped and attributed automatically, with the full history available to auditors on request |
| GL reconciliation | A manual tie-out between the model and the general ledger is repeated at every close | The lease subledger reconciles to the general ledger automatically each period |
| Key-person risk | The logic behind discount rates and modifications lives with whoever built the model | The calculation logic is embedded in the platform and reproducible regardless of who is running it |
| Portfolio growth | New leases, acquisitions, or additional sites require the model itself to be rebuilt or extended | Scales from 30 to over 10,000 leases without a change in process |
Moving a lease register off a spreadsheet is not a single cutover event. It's a sequence that, done properly, gives you a second, independent check on your own numbers along the way.
1. Extract and reconcile the existing register. Before anything moves, every lease in the spreadsheet gets checked against its source contract: commencement date, term, payment schedule, options, and any modifications already applied. Embedded leases hiding in service contracts tend to surface here too, because someone is looking at every agreement properly for the first time in a while.
2. Standardise the data. A spreadsheet built up over several years rarely has consistent field names, date formats, or discount rate documentation across every lease. Standardising these into a single canonical structure, commencement date, term, payment frequency, discount rate basis, options, is what makes a clean import possible, rather than a partial one that needs patching afterward.
3. Load the data and reconcile opening balances. The lease register is loaded into the new system, and the system's calculated right-of-use asset and lease liability are reconciled back to the spreadsheet's last agreed position for every lease. Any discrepancy at this stage is worth investigating properly: it's often the first independent check the spreadsheet's numbers have had in some time.
4. Run a parallel period. For one full reporting cycle, both the spreadsheet and the new system run side by side. Journals, depreciation, interest, and any modifications processed in the period are compared line by line. A parallel run is what turns "the new system says something different" from a surprise at year-end into a resolved question well before the numbers reach an auditor.
5. Cut over. Once the parallel period ties out, the system becomes the system of record. The spreadsheet doesn't need to be deleted, and it's often useful as a historical reference, but it stops being the source anyone calculates from or reconciles to.
6. Build the ongoing process. Migration only pays off if the process that follows it doesn't recreate the same failure mode in a new tool. That means a defined workflow for how a lease modification gets from the property or fleet team to finance and into the system, milestone alerts for rent reviews and renewals, and a monthly reconciliation that happens by default rather than by memory. For the accounting-standard side of transition, discount rate selection, opening balance calculations, and disclosures, see FRS 102 Section 20 transition guide: a step-by-step checklist.
The riskiest part of any spreadsheet-to-software migration is that the spreadsheet's own errors, a wrong discount rate carried forward, a modification that was never properly remeasured, can be imported into the new system and simply continue, now with a cleaner interface around them. A migration only reduces risk if something independent is checking the data as it moves, rather than simply formatting it for a new interface.
This is where LOIS Managed Service changes the shape of the migration itself. CA-qualified LOIS accountants validate the lease data during the move, reconciling it against source contracts and flagging inconsistencies before they're carried into the new system as fact, rather than after they've been reported to an auditor. For finance teams with an upcoming audit, a portfolio already showing signs of strain, or simply no spare capacity to run a careful parallel period themselves, that expert validation during the migration is often the difference between a clean first period close and a stressful one. See FRS 102 managed service vs self-service for the fuller framework on choosing between the two delivery models, and LOIS Managed Service for what the service covers.
At what point should we move off spreadsheets for FRS 102?
There's no single trigger, but the signs tend to appear together: a portfolio approaching 50 or more leases, an audit inside the next 12 months, leases embedded in service contracts alongside obvious property and vehicle leases, one person holding the model's logic, and a steady stream of rent reviews or modifications. If two or three of those apply, the spreadsheet is probably already the larger risk in the room.
Is it fine to keep using spreadsheets for a very small lease portfolio?
Yes, for now. A business with a small number of stable leases, little modification activity, and no imminent audit pressure can reasonably run FRS 102 compliance in a well-built, well-documented spreadsheet. The calculus changes as soon as the portfolio grows, a lease is modified, or an audit date is set, because those are exactly the events a spreadsheet handles least reliably.
What happens to our historic spreadsheet data after migration?
It doesn't need to be deleted. Most finance teams keep the spreadsheet as a historical reference, particularly for the workings behind the original transition calculation, but it stops being the tool anyone calculates from or reconciles to once the new system is live. The system of record moves; the archive can stay.
How long does a spreadsheet-to-software migration usually take?
It depends on portfolio size and how clean the existing register is, but the extraction, standardisation, and loading steps typically take a few weeks for a mid-sized portfolio, followed by one full reporting cycle run in parallel before cutover. Portfolios with a lot of embedded leases to identify, or years of undocumented modifications to unpick, take longer at the extraction stage rather than the loading stage.
Does moving to software mean redoing our FRS 102 transition calculations?
No. The opening right-of-use asset and lease liability calculated at your transition date carry across as the starting position in the new system; migration doesn't reopen that modified retrospective calculation. What changes is how every period after transition is calculated, tracked, and reconciled, not the transition entry itself.
Ready to move your lease register off spreadsheets?
LOIS CA-qualified lease accounting experts can walk through what a migration looks like for your portfolio, including how the LOIS Managed Service validates your data as it moves, with no commitment required.
Explore FRS 102 lease accounting See the full transition checklist