Project cashflow of Exact Online projects based upon invoice terms to be invoiced / already invoiced

For a correct cashflow projection per project on the revenue side on a project with invoice terms (invoice schedule), I need to determine per revenue generating invoice whether it has been processed or not.

I seem unable to find this in InvoiceTerms.

Nor there seems to be a correct way to correlate the SalesInvoices or TransactionLines with the InvoiceTerms. Vague matches based upon description are possible, but are not guaranteed to be correct.

Is there a way to determine for a planned invoice on a project whether it has been invoiced and possibly to what extent?

No, as of May 2019 it is not possible to determine reliably for a fixed price project with an invoice schedule whether it has been invoiced using the APIs.

You will either need to manually and in separate register which ones have been sent or use a different project control package.

@hans.jansen See this topic for an answer to your question, and the related topic Project invoice proposals of Exact Online .