This greatly depends on the project, the participating organisations and their internal rules and practices. It is recommended that beneficiary and partner organization sign a partnership agreement regulating these issues.
In case of secondments, money transfer concerns the cost category research and training, usually based on real costs incurred by the organization which hosts secondments (invoicing is good practice), the researcher usually is still employed by the beneficiary, who pays the living allowances.
In case of Global Fellowships partnership agreements are necessary. The researcher usually is still being paid by the sending institution (beneficiary, according to the GA should employ the researcher for the whole duration of the project), but there are some cases, where the TC institution pays the researcher – in such cases allowances are transferred to TC. Cost category: Research & Training usually is transferred in total for the period of stay in TC (done according to the partnership agreement), transfer of management and indirect costs depends on the partnership agreement.
The MSCA explained by your National Contact Points