Salary slips for at least the previous 3 months, preferably the previous 6 months; AND
Bank statements for at least the previous 6 months; AND
The sponsor's (co-sponsor's) employment contract (if the sponsor is not independently wealthy); AND
The sponsor's (co-sponsor's) most recent P60.
If the sponsor (co-sponsor) is self-employed, owns his own company, or if the sponsor (co-sponsor) does not work, then the employment contract and P60 can be substituted with certified copies of the previous two years' tax returns accompanied by a notarized version of his business accounts.
If the sponsor (co-sponsor) is retired, then the employment contract and P60 can be substituted with a statement from his pension scheme.
If there are disproportionate deposits and withdrawals in the bank statements, they should be explained in the sponsor's letter.
