Dvsa investigation

Hello, im after some knowledge regarding how far back Dvsa can investigate.
I drive casually for a company and have a main job. I have just had information given to me that Dvsa had a complaint regarding my casual driving back in May last year. Im not excusing it but my lack of knowledge back then would raise eyebrows. I have educated myself and as far as I know I am now running a good system and am legal, My issue back then regarded weekly rest on a number off occasions. As far as I know I was having adequate daily rests etc.

thanks

I think they disregard after 6 months but bit 100% on that