Be sure you're distinguishing between transaction dates (Posting dates) and invoice dates.  One affects the GL, and the other affects AR. Also, I'd ask if you are able to narrow it down to certain customers or a specific batch.  There is a utility to recalculate the balances.

It's definitely not due to invoice/transaction dates.  I'm comparing the standard invoice history report with the customer sales by period and have differences for ~6 customers.  I'll have to see if they were all related somehow.  I don't believe there is an 'out of the box' utility to recalculate these period totals is there?  I thought I had read that this could be due to incorrectly closing periods.

National Accounts can throw it off. I'd look for similarities like they all had invoices that were adjusted or had sales tax or something.

There is a checkbox in AR Options for including Sales Tax and Freight in the sales history data.

I only have 5 customers with discrepancies - some of which are national accounts, but I've verified my AR settings that dictate what numbers should be included in the customer sales history report.  Still looking for some kind of pattern

Thanks.

As Rhonda mentioned, the most common difference is when an invoice date does not match the posting date.  The invoice history report will be by invoice date.  Any "by period" reports are based on GL posting date (not the invoice date).

Thanks I was not aware of that.  I still have differences, but less now.  Just wondering - if a period is closed in AR, then reopened to perform a transaction to that previous period, a re-close of that period in AR is necessary right?

So I found that the discrepancies were (in addition to posting date vs invoice date) due to discounts taken on invoices.  While the open invoice tab in customer maintenance was showing no discounts taken on particular invoices, drilling down to their history record showed the discount amounts.  I believe this is because the discount was taken on the payment and not the invoice, but I'm not 100% sure.  Thanks to all for the info provided.

So I found that the discrepancies were (in addition to posting date vs invoice date) due to discounts taken on invoices.  While the open invoice tab in customer maintenance was showing no discounts taken on particular invoices, drilling down to their history record showed the discount amounts.  I believe this is because the discount was taken on the payment and not the invoice, but I'm not 100% sure.  Thanks to all for the info provided.

Discounts taken in cash receipts show as an itemized line with payment reference "DSCNT APPL" on the open invoices tab.

The discount field you see when drilling down comes from the original invoice/sales order. (We don't use this feature so I don't know how it impacts sales reports.)