This can be 2NDFL Help, help shape the bank statement of salary account from a bank, an oral confirmation of the head. And the priorities are exactly in that order. Banks are quite wary of verbal confirmation of income, and not everyone takes such a form of confirmation. Most common statement, which take almost all banks – this reference 2NDFL plus help with the form of the bank. Where the second does not negate the first. 2NDFL should be in any way. Even if it passes on the amount much less than real wages.
Such returns are accepted for review in full. I want to draw your attention that if you work in shifts, a number of banks if they take into account the income from such activity, applies the reduction factor. This applies to seafarers. Income from moonlighting. This is income from activities in which you are engaged in addition to their main job, ie "Part-". But in this case, the bank will require documentary evidence of your activities. Ie must provide an employment contract or in the workbook must be a record that you are accepted into this organization in combination. Of course, it is necessary provide proof of your income.
And this, as mentioned above, a certificate 2NDFL and any further evidence (if the actual wage differs from the official). But there is one more nuance. Income from concurrent banks often accept not in full, but with a certain reduction factor. For example, your income is 20 000 rubles a month, and the correction factor in the bank equal to 0.8.