The OECE Forum on Tax Administration (FTA) has published a handbook explaining participation in the international compliance assurance program (ICAP).
This objective was started in 2018, and is now taking more substance. It is a three-stage process. The taxpayer provides relevant available transfer pricing documentation, and if all relevant jurisdictions and the taxpayer agree, a risk assessment is developed by the tax administrations. The final stage includes a risk graded letter.
The program does not provide absolute certainty, although it may provide learnings into potential gaps, while also providing tax administrations some limited certainty after their comprehensive review.
The handbook, link attached, provides additional details.