PURCHASING MANAGEMENT AND THE IMPACTS OF AMAZONIAN SEASONALITY: A CASE STUDY ON COSTS AND PRICING IN A SMALL RETAIL CONSTRUCTION MATERIALS COMPANY IN TEFÉ-AM

Abstract

This article aimed to analyze the effects of the hydrological seasonality of the Solimões River on purchasing management, acquisition costs, and profitability in a small retail company (EPP) in the construction materials sector in Tefé, Amazonas. From a methodological standpoint, this study adopted applied, qualitative-quantitative research with a descriptive and explanatory character, operationalized through a single case study, with documentary data collected from invoices and management reports extracted from the company's ERP system, covering the period from June 2025 to May 2026. A cost reverse-engineering technique was applied to break down the nominal purchase value of cement, iron, and paint into table price, river freight, road freight, and ICMS-ST (tax substitution), together with the Moving Weighted Average Cost (MWAC) method to determine monthly profit margin. The results revealed an overall gross margin of 15.05% for the period, concealing significant heterogeneity among products: cement, the main item in the portfolio, sustained the lowest margin (11.43%), reaching its floor at the peak of the dry season (September to November), while iron and paint maintained higher and more stable margins throughout the hydrological cycle, revealing a sales-mix composition effect that masks, in consolidated indicators, the real financial fragility of cement during the dry season. It is concluded that anticipating cement purchases during the flood months constitutes a financially advantageous strategy, and its adoption as a permanent inventory management policy for the company is recommended.