I went to my shop till and it said there was about 44mil in there, but after I collected it(and it said I got everything) when I went to my vault I only had about 26mil on hand. I haven't got the tax achievement, so I'm pretty sure it wasn't that. I'm on the mobile version of the site, if that makes a difference. Oh, and my till now says zero, so that 18mil is gone it seems. :/

Edit now that I'm on my laptop: Double checked the totals from the shop log and what's in my vault(since I threw the 26mil in there before checking for the tax achievement), vault is at about 612mil when I know I was at around 568mil earlier yesterday, not 586. So it seems the 18mil went straight to my vault?

Edit again: I feel dumb now, haha. I just realized that when I went to my vault, I had clicked on it in my history on my ipod. But apparently I had clicked on the page where it was loading a deposit, and since my last deposit was about 18mil, it put that much in my vault. No missing points or any glitches. xD