Documenting Your Professional Experience
That's all you need. Maintain the statements from both accounts; they are the valid legal proof that you offered your professional services to them. Now, take a closer look at every communication you had with your organization. Streamline the ones that include details about your roles, tasks to be delivered, skill sets you worked on, projects you handled, and any appreciation you received. Keep printouts of all such communications. It can be through emails with a company email ID or on any letterhead. Other than that, the Form 16 is another proof accepted by all companies, so keep it ready.
Finally, when you leave this organization, you may or may not get any communication from them. Hence, write a detailed testimonial for them, appreciating the time and experience you had with them. Please mention all your roles and duties delivered and thank each person to whom you reported. Keep a printout of it with you. You may or may not get a reply from them. In case you are lucky to get a reply, probably a similar thanks, keep a printout of the entire conversation. That should do you good. Keep a very grateful and non-threatening approach throughout, especially during your exit process.
Wish you all the best!
Regards,
(Cite Contribution)