1. For a quick total, open Profit and Loss. Go to Reports, search Profit and Loss, and set your date range. The first income line, before any discounts or cost of goods sold get subtracted, is your gross sales for that period.
2. For a breakdown by customer or item, run a Sales report instead. Search Sales by Customer Summary or Sales by Product/Service Summary under Reports. These total every sale before deductions, which is what you want if you're after gross sales specifically, not net.
3. Watch for discounts and returns hiding in the same report. QuickBooks sometimes nets a discount or return against the sale on the same line in a summary view. If you need the true gross figure split out from those deductions, run the report at the transaction-detail level instead of summary.
4. Set the date range to match what you're reporting on. Gross sales only means something next to a specific period, monthly, quarterly, or annual, so match the range to whatever you're comparing it against.