This study aims to analyze the administrative procedures for submitting Periodic Value Added Tax (VAT) Returns (SPT Masa PPN) via the Coretax Administration System application at PT Mutiara Solusi Cipta, a tax consulting firm based in Sidoarjo. The research is motivated by the digital transformation of tax administration implemented by the Directorate General of Taxes (DGT) through the adoption of Coretax starting January 1, 2025, replacing the previous separate systems of e-Faktur, DJP Online, and e-Nofa. A descriptive-qualitative approach was employed, with data gathered through direct observation during a field internship (PKL). The results indicate that the administrative procedure for reporting Periodic VAT Returns at PT Mutiara Solusi Cipta using Coretax involves several stages: document receipt, data completeness checks, data input and verification on the Coretax portal, preparation and submission of the return until the Electronic Receipt Proof (BPE) is obtained, and work archiving and recapitulation using Microsoft Excel. Coretax is considered to offer greater convenience by integrating all tax services into a single platform, thereby reducing the need for inter-system coordination and the risk of data discrepancies. However, technical issues—such as internet connectivity disruptions and unexpected automatic system logouts—were still encountered during implementation, potentially hindering data input and verification processes. The study concludes that the implementation of Coretax supports the creation of tax management that is increasingly structured, centralized, and aligned with information technology advancements in the taxation sector.