While it is possible to use a custom field to record the job payment status, vWork was never intended to operate as a full finance package.
We suggest that you sync your invoices with an accounting system like Xero or QuickBooks to record and track payments and monthly statements.
You can find more information about our QuickBooks Online, Xero, and MYOB integrations here.
You can also export all of your invoice information as a CSV for use with Excel or other finance packages. You can find out more information about generating invoice reports here.