Hi there, Robin. The requirements for timely filing generally vary from insurance company to insurance company. However, most companies we've assisted clients with in the past have accepted screenshots of the claims tab in patient workspace. This should show them the bill date for the claim.
Let me know if you have any further questions!
When you send out a claim it enters the date the claim was submitted on the claim. In addition it puts a bill date which would be located in the claims tab on that specific claim. If it was sent out electronically, you will have your reports that would indicate the date it was submitted.