Delete or void Invoices (don't make mistakes permanent)

Absolute MUST to edit an invoice or delete. ALSO - Why can’t I create my own invoice numbers???

Here’s a REAL LIFE SCENARIO. I sell a product to small stores. I go in, I give them a PAPER INVOICE (they will NEVER give me an email address and they will NEVER pay electronically), they pay me cash or check. I need to record that in HubSpot, but can’t. Why? Because my invoice book numbers might be 1000-2000 and another salesperson’s might be 3000-4000, but HS insists on a single sequence.

Also, why does recording a payment REQUIRE an email address?? Makes no sense.