The document provides guidance to beneficiaries of EU research grants on avoiding common errors in cost claims. It lists the 10 most frequent errors, including: costs not substantiated or linked to the project; unapproved use of third parties; improper depreciation charges; incorrect use of indirect cost models; including ineligible costs in indirect cost pools; improper calculation of personnel productive hours; and incorrectly charging hours worked. Beneficiaries are advised to carefully review financial rules and check that all claimed costs are real, paid, project-related, and properly calculated and documented to avoid errors and ensure timely reimbursement.