How to Convert FRS 102 to US GAAP

FRS 102 and US GAAP share some common DNA (both are accruals-based, both use similar income statement structures) but they differ materially for UK companies entering US capital markets, raising investment from US PE and VC firms, or preparing for acquisition by a US buyer. Revenue recognition, lease accounting, development costs, and deferred tax all work differently.

This guide covers the process from start to finish.

Step 1: Understand the Nature of Transactions by Account

Start with the UK company’s trial balance under FRS 102. For each account, document what types of transactions actually flow through it. This step confirms what the company is actually doing in practice, not what the standard technically requires. You may find that certain transactions are not being tracked or measured in a way that will support US GAAP reporting, or that materiality thresholds differ between the two frameworks.

A single FRS 102 account may contain mixed transaction types that need to be split under US GAAP, or may require different accounting treatment depending on the nature of the transaction within it.

Step 2: Build the Chart of Accounts Bridge

Once you understand the nature of transactions, map every account to a US GAAP financial statement line. This is not always one-to-one. Some FRS 102 line items need to be split (deferred income between current and non-current, for example). Some US GAAP line items need to be built from multiple FRS 102 accounts.

The output of this step is a chart of accounts bridge document that shows, for each account, its FRS 102 classification and its US GAAP classification. This document becomes the foundation of the conversion workbook.

Step 3: Document Current FRS 102 Accounting Policies

Document the accounting policy for each material area: how revenue is recognized, how leases are classified, whether development costs are capitalized, how financial instruments are measured. Cover everything from initial measurement and recognition through subsequent measurement. Validate that the existing accounting treatment reflects what is actually being done operationally, not just historical practice or theoretical standard requirements.

Step 4: Define the Proposed US GAAP Treatment

Engage a US GAAP expert to write up the proposed US GAAP treatment for each material area. The goal is normally to stay as close as possible to current practice where US GAAP options allow, while benchmarking against peer company treatments in your industry. This step produces a clear technical definition of what the company will do under US GAAP before you calculate any adjustments.

Step 5: Identify the Material Differences

With both the FRS 102 practices and proposed US GAAP treatments documented, identify where they diverge. The differences vary by company, industry, and transaction complexity. Common areas to examine include revenue recognition methods, lease classification and measurement, treatment of development costs, goodwill amortization, and financial instrument accounting.

Step 6: Calculate the Adjustments

Engage a GAAP conversion specialist to translate each identified difference into practical next steps: how the calculation will be made, what supporting files and subledger records are needed, and how the adjustment will be documented in the conversion workbook. This is the work I walk clients through during my GAAP Summit, which helps upskill your team alongside completing the technical conversion.

For each difference, calculate the adjustment required to restate from FRS 102 to US GAAP. Quantify the impact for each period being converted (typically a two-year comparative period plus opening balance sheet for audit purposes).

The adjustments are captured in the GAAP conversion ledger, which produces a US GAAP trial balance that rolls up to the US GAAP balance sheet and income statement. Each adjustment column is labeled and traces back to supporting documentation.

Step 7: Prepare the US GAAP Financial Statements

With the conversion workbook complete and the adjustments documented, prepare the US GAAP financial statements. For material areas (revenue recognition, leases, financial instruments), full technical accounting memos support the audit package. These memos explain the FRS 102 treatment, the US GAAP treatment, the basis for the adjustment, and the journal entry required.

The financial statements, together with the conversion workbook and technical accounting memos, constitute the audit package.

How Long Does It Take?

The timeline depends on the scope and complexity of your conversion. Identifying and documenting material differences typically takes eight to twelve weeks for a single-entity UK company with straightforward operations. However, calculating adjustments takes considerably longer, especially where significant lease portfolios, complex revenue streams, or multiple entities are involved. Preparing audit memos and supporting documentation for the audit package adds further time.

Working with a GAAP conversion expert and US GAAP specialist accelerates the timeline, reduces the burden on your internal finance team, and minimizes risk to the audit. You get the technical expertise without consuming resources that your team needs for operations.

For a transparent view of what a full conversion costs, see my pricing page.