Which Safe Harbour Should You Test First?

Write down the tested jurisdiction, fiscal-year dates and collecting rule before choosing a worksheet. Gather the source data and previous election history. Ask whether the relief is available under the applicable domestic framework for that period. A familiar safe-harbour name is not enough: eligibility, accounting sources and conditions still need to be established.

For project planning, create a screening table listing each potentially relevant relief, its prerequisites, the evidence available and the person who will decide whether it can be claimed. Mark unresolved conditions clearly. The purpose is to avoid preparing an unnecessary full calculation where a valid simplification exists, while keeping an alternative calculation route open if the screening fails.

The January 2026 OECD package includes a Simplified ETR safe harbour and an extension of the Transitional CbCR Safe Harbour. These are different routes. Their periods, input definitions and eligibility conditions need separate attention. The package also addresses substance-based tax incentives and parent-regime relief; none should be treated as a universal replacement for all Pillar Two analysis. The Simplified ETR route generally covers fiscal years beginning on or after 31 December 2026; optional use from 31 December 2025 depends on Box 7.4 and the applicable domestic rules.

For example, a fictional team has reliable CbCR data but incomplete GloBE adjustments. It should first establish whether the relevant CbCR route is actually available for the jurisdiction and year, including its history conditions. If it is not available, the team cannot simply relabel the same figures “Simplified Income” and claim a different relief. Identify the preparation work that the alternative route requires.

An efficient internal sequence is to screen clearly relevant reliefs using information already available, confirm their conditions, and then prepare the remaining calculation. It is not a legal ranking that overrides the rules. Keep QDMTT relief, parent-regime relief and incentive adjustments distinct because they address different parts of the system. Seek technical input where elections interact or the correct sequence is unclear.

Record which tests were considered, why a test was unavailable and the evidence for any successful claim. Do not tick an eligibility confirmation merely to make a calculator produce a result. If the test fails, retain that outcome and move to the appropriate next calculation. A failed screen can still save time by defining the information the full calculation needs.

Bring us the tested year, jurisdictions, available reporting packages and any previous claims. We can help identify which reliefs deserve examination first and where local confirmation is required. The goal is a documented route through the rules, not the largest possible number of ticked boxes. Keep the registration and reporting calendar running alongside the calculation work, even where a safe-harbour outcome appears likely.