Is there a voucher to pay self employment tax? If not how do I go about sending payment?

[VolvoGirl]

The current self employment tax?  That is included in the refund or tax due on your tax return.  It is on line 57.  You don't pay it separately.  

Or do you need estimated quarterly payment slips for next year's 2016 return?

[Opus 17]

If you want to mail a check for 2016 estimated tax payments, there is a voucher to go with the check, at the bottom of form 1040-ES (back pages) https://www.irs.gov/pub/irs-pdf/f1040es.pdf

Or, you can make an online payment directly to your tax account in which case no printed voucher is needed.

https://www.irs.gov/payments