Can I create multiple invoices for a single Work Order in Zoho FSM ? How to create multiple invoices in Zoho FSM ?

Can I create multiple invoices for a single Work Order in Zoho FSM ? How to create multiple invoices in Zoho FSM ?

Yes. You can create multiple invoices for a single Work Order.
While creating an invoice, select only the services you want to include and leave the remaining services unbilled. You can create additional invoices later for the remaining services.
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Each invoice must include at least one service line item. 
Refer to How do I create an invoice in Zoho FSM?
Repeat the process to create additional invoices for the remaining services.