You can make a payment using the retainer amount in ArchiOffice/EngineerOffice. To do so:
1. From the Billing > Outstanding tab, open the Transactions screen for the relevant client.
2. Click the Retainer option.
3. You will be prompted to make a payment from or to the retainer account for that client. Click From to make a payment using the retainer. The retainer details populate the screen.
4. You can specify the retainer Amount to Apply as payment or use the full retainer amount.
5. Click Apply on the grid against the invoice on which you want to make the payment.
6. Click Done.
7. To see the retainer payment on an invoice, go to Projects > Billing > Options screen.
8. Check the Show Retainer box and select the desired invoice template. 
9. Click New to generate a new invoice.
