How can we create an label, value detector? I am trying to implement an text detector using MaskRCNN such that the model detects the label and value as shown in the image below.

Detecting the same is easier for fields like page date and order no. but fails for invoice number and salesman shown in image below. Is there any pretrained models for the same? or some other technique that might help.
Here is a paper doing exactly what you want with detailed explanation of architecture.

There is not much sense of me doing a TL;DR here because they have some special labeling of data etc... but the gist of it is LSTM if you do some pre-processing steps and get your data in right format.