Yes, Timekeeper ID is ALWAYS required on Expense Line Items for Lawtrac clients. At this time, Lawtrac is not able to accept "expense" line items without the timekeeper information.
If you are not sure which timekeeper to use, we suggest you pick one timekeeper for all your expenses OR you can create a new timekeeper, with the name, "Expense Timekeeper" (and TK ID "ET") and have that authorized by your client. Most firms have an Expense Timekeeper with a high rate (i.e. $1000 per hour).