Ripple Labs has issued a Gateway Bulletin on the Partial Payment flag which describes the flag and best practices around balancing activity on and off the ledger. The tfPartialPayment flag is set by the sender to specify a payment where the beneficiary can receive less than the specified amount.
Gateways are encouraged to implement best practices and understand the Partial Payment flag to mitigate errors that can result in fraud if undetected.
To view this bulletin, please visit: https://wiki.ripple.com/