Damásio, Bruno Miguel PintoSilva, Rodrigo Miguel Vidal da2025-11-112025-11-112025-10-29http://hdl.handle.net/10362/190490Dissertation presented as the partial requirement for obtaining a Master's degree in Data Science and Advanced Analytics, specialization in Data ScienceThe automated extraction of important information from different types of documents, especially invoices, is essential for improving business operations and increasing efficiency in finance. In the past, this was a time-consuming and error-prone manual task. Recently, progress in deep learning and transformer-based learning has renewed interest in automating this work. It offers promising solutions for smart document processing. This thesis tackles this issue by focusing on fine-tuning LayoutLMv3, a transformer-based model, to extract key fields from Portuguese invoices and receipts. The main goal of this research is to adjust LayoutLMv3 for a custom dataset of 813 invoice and receipt images in Portuguese. The model will be trained to clearly identify and extract important details like company name, address, date and total amount. This information is essential for keeping financial records and streamlining workflows. To prepare the training data, we first use Tesseract for an OCR step. This extracts raw text and their corresponding bounding box coordinates from the images. After that, we use a custom algorithm to accurately label text categories that either match or closely resemble the predefined annotations. This process ensures the dataset is properly formatted for LayoutLMv3's multimodal input needs. After the preprocessing and labeling steps, the LayoutLMv3 model is fine-tuned and evaluated. Its effectiveness is measured by comparing its performance to a well-known commercial solution, Google Document AI. This comparison aims to show the practical use and limitations of a custom-trained open-source model in a real-world scenario. The results show that Google Document AI outperforms the fine-tuned LayoutLMv3 model by a large margin. However, the findings offer valuable insights into the strengths and weaknesses of fine-tuned Transformer models for extracting information from documents in a low-resource language context and semi-structured document types. Additionally, this research can help improve automation in financial processes, reduce manual work, and provide a solid framework for similar document understanding tasks in different industries.engOptical Character RecognitionKey Information ExtractionInvoicesMultimodal Machine Learning ModelsSDG 8 - Decent work and economic growthSDG 12 - Responsible production and consumptionSDG 13 - Climate actionSDG 15 - Life on landmaster thesis204070830