It's a nice overview article for anyone interested in the topic of IE from financial documents. However, for industrial level solutions Tesseract does not cut it. Abbyy is the best OCR engine on the market currently. Receipt IE works just fine with rules supported by a small BiLSTM as fallback just because receipts do not contain a lot of text. With invoices this approach is suboptimal. On a general note no DL approach will give you fast and high enough results just because any advanced network would be too slow and too generic. If extraction takes more than 5 sec. it is hard to sell such system.