If they don't have evidence, how can they claim a deduction?

How? a number is told to me and I list it.  To defend it is another matter.

Or are you referring to the Is the evidence written question? 

yes, this question is interesting to me too.

Regardless, taxpayers have always been required to be able to support deductions claimed on their returns, whether there is a specific question about it on the return or not.

Since support is required then it is odd that the IRS asks taxpayers to self-incriminate.

I know a client won't file 1099s despite my advice, should I answer No to the question on Sch. C about intention to file them.