Yes your suppose to claim your tips every night but there are ways around it. The IRS figures your going to make a certain amt per hour in tips, add a little to that figure, and thats what gets claimed.
I'll be frankly honest, I don't know a single waitstaff person who has ever claimed all of their tips. Maybe there is someone out there, surely there must be, but it's a legitimate argument that most don't claim it all.
The IRS mandates (or at least did at the time I waited tables) that 8% of gross sales be reported. Restaurants vary as to how they go about this. Some just take a flat 8% off the sales and divide it by the waiters/waitresses who worked that day or divide it then by hours worked and waitstaff, etc... Others require weekly tip reports. One I know of had the waitstaff figure up only their sales for the day and they then turned in 8% of only their sales each and every shift they worked (much fairer system really).
Some restaurants allocate tips on the W2's at the end of the year, others don't.