I cannot find the following options in the Retainer Invoice:
1. Product selection in Table rather than just text fields.
2. Fields in Table like HSN/SAC
3. Payment reminders
4. Tax
5. When Retainer Invoice is paid, convert Retainer Invoice directly to Invoice and mark it as paid.

I can understand that this is just an advance payment. Still, we critically need these options to be implemented as soon as possible.