What if I don't want to build a sync? Can I just reconcile manually?

You can, but it scales poorly. Manual reconciliation takes 2–3 days at month-end and introduces human error. A one-way sync takes 4 weeks to build and then runs in minutes every week. At 50+ invoices per month, sync pays for itself in reduced reconciliation time within two quarters.

Which system should be my invoicing source—CRM, accounting, or billing?

Choose the system where you already have customer and project data. If you manage deals in a CRM, create invoices there. If you work directly in accounting, create invoices there. The key is that invoices flow outward (to chat, to accounting), never backward. Avoid creating invoices in multiple places.

What if a payment is received but the invoice hasn't been sent yet?

This is rare but possible (prepayment or advance retainer). Create the invoice in your CRM immediately when payment is received, mark it as "paid," and sync it to accounting. The invoice ID and amount will match the payment record in QB, and your audit trail will show the correct sequence.

How do I handle invoices sent before I had a unified system?

Import them as historical records into your CRM (or accounting software) with a status of "closed" or "archived." Create a GL adjustment entry for any outstanding AR that isn't reflected in your current GL. Run your reconciliation script on the last 90 days of new invoices only, and carry forward the historical discrepancy as a one-time adjustment.

Invoice Reconciliation Multiple Systems