Confirmation of employment must be presented in original letter from an Employer — this means that the letter must be written on a company letterhead and fixed by a company seal and signed by the relevant company official. Letter of employment signed by an Applicant can not be accepted as a proof of employment.
For pensioners — a pensioner certificate
For students — a formal letter from the educational institution.
The Russian income tax report 2 NDFL can be considered as a proof of employment/may be asked at the First Secretary: Immigration’s discretion.