I work a regular salaried job. I did a side job and earned $825.00 on 5-23-18. I figured this was going to be my only side gig for the year, so I thought I would pay taxes at tax time (April 2019), since the taxes on that didnt meet the IRS $1000 threshold for an Estimated Tax Payment.

I just found out I got another side gig for $7500.00 that will be paid in late Oct 2018. This job will require that I purchase many materials with the money, and I hope to keep the remainder. How do I pay the taxes on this? What about the earlier job that I didnt pay for yet? (now that my total tax bill will be over $1000 for the year)

Side note: Ive also read that you can pay for the taxes by adding an adjustment to my W4 with my salaried job, but I dont know how that works with my situation, if at all.

Thanks!