Invoices paid by agent from rent can be allocated to specific supplier

To be able to track spend with a specific supplier would like the option then when receiving rent via an agent, if they have added an invoice that they paid I would like the option of selecting the Supplier instead of it being booked against the Agent so I can clearly see who did the work against the property. 

It also allow me to compare pricing between suppliers for similar work such as Gas Certification, one supplier may charge £78 whilst another will charge £60.