I already have taxes coming out of both my full time and part time pays why do I need to fill out Part 4(c) with an additional amount for my full time job? Isn't that having triple taxes withheld for only 2 jobs?
how much are you expecting to make at each job?
read the instructions closely - best to complete 4c on both jobs if the part-time job is at least half the pay of the full time job. Otherwise, filling out line 4
b
for the fulltime job and leaving 4b blank for the part-time job is the way this is supposed to work...
these are 'withholdings' only - it is not tax. if the withholdings are too high compared to the tax calculated on your tax return, that is what creates the refund. But if you follow the W-4 instructions closely, the refund / tax owned will be minimal.
The balancing act between several jobs worked at the same time is delicate ... so if all the jobs are having not having enough withholdings overall when you choose SINGLE on all the W-4 forms then you need to adjust somewhere so you have enough withheld. The W-4 has that worksheet to help with the needed adjustment but the IRS has a better/easier tool ... Tax Withholding Estimator
It is important to understand that the W-4 generates an estimate of your income taxes that your employer uses to determine your withholding. For a single person, that includes the assumption that they qualify for a $13,850 standard deduction (in other words, the first $13,850 per year or $266 per week is tax-free). If you work 2 jobs and don't make adjustments, each W-4 will assume you have a $13,850 standard deduction, so you will be under-withheld by as much as $5000 over the course of a year. That will result in a difficult tax bill to pay plus late fees and interest.
You should carefully read and follow the instructions on all 4 pages of the W-4 and prepare both forms at the same time following one set of instructions. If you have too much withheld, you will get the difference back as your tax refund.