PND 91 needed for new Non-B visa?

[Millian]

Hello,

Currently in process of getting a new Non-B visa for a new Job.

The agency is asking for my PND 91 from 2020, which I don't have and never did.

I've asked the company I worked for in 2020 if perhaps they submitted on my behalf, but they confirmed they don't submit for employees.

I've worked for 6 different companies in Thailand, but don't recall ever being asked for a PND 91 for a visa application.

I also don't believe I have ever filled in & submitted a PND 91 either. My employees have always deducted the tax each month from my salary, so I presumed a tax return was not necessary?

So I'm wondering why I'm being asked for PND 91 for this application?

Either:
a. In the past my employers have submitted PND 91 on my behalf each year.

b. Its not actually required?

Any insights?