Here are the steps to select and mark multiple Invoices as paid in Moon Invoice. 

1. Launch the Moon Invoice application on your device or tap on this link.
2. Navigate to Sales ➜ Invoices.
3. Use the Status Filter to select Overdue invoices.
4. Tap the Edit icon to enable selection mode.
5. Select the invoices you want to mark as paid.
6. Tap Payment ➜ Choose Mark as Paid.
7. Select the preferred payment method (e.g., Cash, PayPal, Apple Pay, etc.).
8. All selected invoices will now be marked as paid in a single action.