Digital-forms are commonly used for collecting structured information from users. However, filling digital-forms that include a large number of fields is tedious and error-prone. Auto-filling form fields for the user is highly beneficial for improving user experience and potentially collecting more valuable information (in cases where not all fields are mandatory). Online E-commerce marketplaces quite often utilize such forms to collect listing attributes from sellers. In this work, we describe Form-BERT -- a Transformer-based model which is optimized for auto-filling listing attributes given the following inputs: free-text, list of known attribute names, and zero or more attribute values. Form-BERT can be further used iteratively to leverage filled out attributes as the form filling progresses.