With my 1040, I also filled out a form 9465 to make installment payments on what I owe. I wanted to make an initial payment of $4000. How do I do that?

[AnthonyC · Accepted solution]

If you told Turbotax during the installment application (assuming you filed a Form 9465 through TurboTax), then a Form 1040-V voucher should have printed along with your return for that amount.  You should send your check for the $4,000 along with Form 1040-V to the IRS.  It won't need to be received before April 18th, as long as its postmarked by 4/18, you will not be charged interest/penalties on that amount - though, you still will accumulate on the rest of your unpaid balance. 

Also, you don't have to use the check/voucher method.  You can make the same payment online directly at the IRS website if you wish and you can just ignore the printed voucher -

https://www.irs.gov/payments