@KathrynScofield - when you have discussions with this customer set YOUR deadlines based upon days after the customer provides their data.
Do not allow yourself to be backed into a corner where the customer only provides the data on July 4 at 5pm then has the expectation that you'll work all holiday to get the data ready.
For example, ""Within xx days of receiving access to your QuickBooks data which has account numbers already assigned"" we will import the general ledger accounts (no history) to Sage 100.