When does one pay taxes when converting IRA to a ROTH IRA?

[irstaxpayor]

I am considering converting my small IRA into a ROTH IRA. Can I do that in the middle of the year and report it on line 15b as a taxable distribution and then pay the taxes for the year I am converting it in? 

The IRA is a residual converted amount from a company 401k done a few years back.

My income is such that I may be able to cover the taxes owed for 2017.

[Opus 17]

If you perform the conversion any time in calendar year 2017, the taxes will be calculated and paid on your 2017 tax return which is due April 15, 2018.  To avoid a penalty for underpaying your taxes during the year, the amount you pay into the system (combination of withholding and estimated payments) should be at least equal to 110% of your tax liability (line 63) from this year.  Your withholding may already cover it, or you may need to make an additional estimated payment.  If you need to make an estimated payment to bring your yearly payments up to the needed amount, the deadline would be September 15 for a conversion that happens between now and August 30.  You can make a payment at www.irs.gov/payments, make sure to select "2017 form 1040-ES" as the reason.

[fanfare]

If your income is low, (unemployment, for example), that's a good time to convert a portion of IRAs to Roth IRAs.