How to split a bill between company and I?
 

I am renting a car for 10 days, 7 of those days are covered by the company and 3 of those days are myself. It is a road trip whereby I want extra time to visit more cities during the way back.

The first 7 days will be on company time and the latter 3 days are personal vacation. The issue is that it is a road trip so dropping off the car between 2 contracts is not an option.

Also my company is very particular that the credit payment amt needs to match the bill amt. So there a possibility to rent a car for 7 days, and then have a "late fee extension" with the car company and I pay that out of my own pocket?

What kind of options are there?

This is going to be very difficult, if not impossible to do. The only way we can think of to do this is to break it up into two one-way rentals--one for the first 7 days, and then another for the last 3 days.

The company likely won't accept a one-way, likely using a contract rate with an intercity mileage charge, when it expects a simple roundtrip like presumably everyone else traveling.

The assumption is that it’s already a one-way rental during the first 7 days. If not, then the OP could just return the company rental after the business portion of the trip and pick up a personal one-way rental for their road trip.

The OP implied the leisure activities are mid-trip. Ex fly into ORD and drive 2 hours to the office in WI, then stop in Madison on the way back to ORD.