I'd have him register the car. But have him sign a bill of sale with registration as part of the deal. A fair deal would be to deduct registration/taxes off the agreed upon sales price. EDIT: I would also go with him to the DMV to see if there is a way to expedite the process by having him pay the taxes and then them allowing you to register it in your name (and pay taxes again) without having to wait for a title in his name to arrive. Just a thought, never know.

Bottom line... this guy screwed up signing the title and now wants to get out of paying taxes. There's no way around that. He isn't the registered owner of the X5 until the title is in his name, even if he is the owner legally (assuming he has a bill of sale).

If I were in a position to buy that X... I'd try to make it happen. Hard to find a clean 61,000 mile imola red 4.6is. It's going to come down to how much you want that X. It's not going to be a quick or easy transaction... but if you really want it, would be worth the work in the end.

If the guy gives you guff, or doesn't want to be bothered registering it, then yes... as upallnight says, just walk away.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)