If you have a Collective with funds in its balance, you may use that as a payment method when contributing to another Collective within the same Fiscal Host. There are no fees for this payment method. Simply make a contribution to the payee Collective and select the payer Collective as your payment method during checkout.
We are working on the functionality to enable Collectives to give directly to Collectives in a different host (see #3190). As a workaround for now, use the following process:
Contact the Fiscal Host of the payee Collective and ask them to submit an expense to the payer Collective for your donation
The payer Collective will approve the expense and its Fiscal Host will pay the Fiscal Host of the payee Collective.
The payee Fiscal Host will then allocate the money to the payee Collective manually using 'add funds'.