@ngosyhan I would not defer the tax-unless they really really don't have the money--first you will have to remember when preparing next years return, that the tax was deferred then explain to them that they owe more because of the deferral and lastly what if you forget to add back the deferral and they have to pay a penalty--who do you think they are going to blame!
I allowed a deferral of some of the SE tax for my client. ProSERies added the deferred amount as credit/payment. This was disallowed by the IRS and the clients refund was reduced by the deferred amount. This should not have been allowed by the program.