You can hide payment options you don't use, such as a voucher or custom payment, directly on the POS.
On the Master iPad, go to Settings > Payment > Manage Payments.
Turn on Enable Payment Management.
Tap Edit.
Turn off each payment method you don't want to show.
Tap Save.
Run Master Sync so the Slave iPads show the same payment options.
Related
To add your own payment type, see Custom Payment Methods.
To turn cash on or off for online orders, see How to switch ON or OFF CASH payments (COD).
Surcharges are set separately. See Surcharges on Nomni POS.