The 2307 form shows the withholding tax paid by a withholding agent.
This certificate is accounted as an asset by the taxpayer, and are considered as income tax prepayments – as they are deductible from income tax due of the taxpayer during a quarterly or annual income tax return.
It functions as an income tax credit or the "advance income tax" of the payee.
So, basically, the user will send this certificate to all the sources he withheld taxes from. The source needs this certificate for documentation, and for filing of income taxes.