There are cooperatives that can invoice instead of the consultant. It includes paying an entrance fee, a monthly fixed and a percentage on the invoice.
The Social Security cost, withholding income tax and the deduction on account of the payment of the Corporation Tax are deducted from the invoice amount.

This option may be of interest when billing does not involve a high amount, given the commission on invoiced volume. It is useful in occasional jobs in which you do not want to incur any risk with Social Security if you have decided not to register as an independent.

The cooperative only gives you discharge in the general regime (non-autonomous) the days that have been worked.
Examples of these cooperatives are:

In these pages, it is thought about the functioning of these organizations:

Information prepared by Enrique Bravo