Background verification fail if I show less salary?

I worked total 3 nos company. Now I'm joining a MNC. At MNC I have written exact salary of my last company. But for first 2 company I have written my In hand Salary x 12. For first 2 company I don't know my CTC. Because after joining 6 months later they give a salary hike but they don't provide me my salary break up, increment letter even Salary slip. They don't provide salary slip. So in MNC background verification I multiplication my In hand with 12. And show my less salary. So conclusion is my last company salary is shown perfect but previous 2 company it is shown less salary. Will my background verification will fail?

Hi,

In case of verification what you wrote has to match with the salary data provided by that first two companies. In case of any query raised you can explain.

Can they terminate me for this reason. My last company salary is perfectly ok.
And at the day 1 should I tell this problem to HR? Should I disclose this problem by myself or after background verification if they ask then I will tell them?

Hi,

My suggestion is that you can inform in advance.

Is there any possibility that my background verification will fail? I already explained the reason. Though my last company salary is perfectly ok & I got hike on my last salary.