Yes, you can assign a job to an existing invoice. If your business creates the invoice first, waits for payment and then does the job, then you can assign the job to an invoice that’s already been generated.
This can be done when creating a job or when editing an existing job, use the drop down in the Financials Section > Invoice to select the invoice that you would like to be attached to the job;
To do this through the App, when creating a job or when editing an existing job, use the dropdown under Add Quote or Invoice > Add Existing Invoice to Job, to select the invoice that you would like to be attached to the job;
An invoice can also be converted to a job.
In the App, go to Accounts > Invoices > select the Invoice > Convert to Job (bottom row of the invoice). The new job page will then appear, to finalise the job creation with the invoice attached.
In the Web Portal, go to CRM > Invoices > Edit pen for the chosen Invoice > Convert to Job (bottom right of the invoice). The new job page will then open, to finalise the job creation with the invoice attached.
