The IRS does not make them declare 8% of there tips. They are required to declare 100% of there tips, 8% happens to be a magic number where they seems to leave u alone and not audit, but thats changing. Many of the chains are now allocating tips on w-2s, i had claimed 8 or 9% one year and the company i worked for decided that i needed to claim more so the added more in, how nice of them
The irs is now starting to compare the cash tips % to the credit card tip %. Its not like the companys want them to claim more tips, when they do that the company has to pay more in taxes (ie the matching taxes, -S.S., fico etc etc)