Visa rules state we must give provisional credit for losses from unauthorized use within 5 business days of notification of the loss (which is the same as a consumer card) if processed over the Visa network. If we give provisional credit, do we still get the 90 day limit to investigate?

Reg E does not apply to business cards so you are not constrained by the investigation timeframe limits of Reg E. VISA does not have perscribed timeframes for completing an investigation only for completing actions within the chargeback process.

Fraud related chargebacks must be filed 120 days from the date of the tranasction. The merchant may represent within 45 days following the chargeback. The bank has 45 days following a representment to file Pre-Arbitration against the merchant. If the merchant contests, the bank may file Arbitration within 30 days of the PRe-Arbitration filing.