A Benchmark Workshop on Celtic Sea Stocks (WKCELTIC) to evaluate the appropriateness of data and assessment parameterization of three stocks: Cod in divisions 7.e–k (cod.27.7e–k), Whiting in divisions 7.b–c and 7.e–k (whg.27.7b–ce–k) and Haddock in divisions 7.b–k (had.27.7b–k). The procedure to calculate catch in number and weight-at-age were revised in a data-compilation workshop. The approach was standardized and streamlined across countries and stocks as much as possible using a common R-script, ensuring transparency and reproducibility. Natural mortality and maturity-at-age were updated. For all stocks survey indices were calculated based on the VAST software in attempt to address issues of missing survey coverage in some years. As before the indices were based on the IGFSWIBTS- Q4 and EVHOE-WIBTS-Q4 surveys. This resulted in the new indices having a higher internal consistencies among stocks compared with the conventional calculation that had been in use previously. The assessment framework for all stocks was based on SAM (https://www.stockassessment.org) because of availability, reproducibility, statistical handling of discard estimates where needed and familiarity of the external reviewers with the method and software. The approach consisted of gradual introduction of new data to identify the influence on stock dynamics and configuration of the model setup based on diagnostic comparisons. The reference points were updated based on the final results using ICES standard procedures. Forecast is produced internally within SAM to ensure consistency.