In general, the campaign or political party that receives a contribution is responsible for reporting it. However, individuals or groups making in-kind contributions should notify the campaign of the date and value of any in-kind contribution to ensure it gets reported accurately.
Any contributions made by a PAC to a candidate must be reported by both the PAC making the contribution and the campaign receiving the contribution. PACs are subject to extensive reporting requirements, including reporting all contributions received and all contributions or expenditures made by the PAC.
Corporations, including many 501(c)(4)s, are prohibited from making contributions to federal candidates.