What is unapplied cash in accounts receivable?

Unapplied cash is an AR reconciliation problem that compounds over time. When a customer pays without a clear remittance reference, or pays a round number that doesn't match any open invoice exactly, the payment sits in a suspense account until someone manually investigates and applies it. During this time, the AR aging report may still show those invoices as overdue, triggering unnecessary follow-up.

The most common sources of unapplied cash: wire transfers or ACH payments with no invoice reference, checks with memo lines that don't match invoice numbers, overpayments where the customer paid slightly more than owed, and payments that straddle multiple invoices without a remittance breakdown.

Best practice: request remittance advice from every customer at the time of payment, especially for ACH and wire. A simple email template requesting 'Please include invoice number(s) and amounts on your payment confirmation' eliminates most unapplied cash situations before they occur. For customers who consistently pay without references, a payment portal that lets them select which invoices they are paying solves the problem structurally.