Question

Compute Mike's estimated tax payment for the fourth quarter. He is self-employed and he expects to earn $20,640 this year. His estimated income tax rate is 18%. For self-employed persons, social security tax is 12.4% of wages up to $106,800, and Medicare tax is 2.9% of all wages

Answer 1

so, add up the taxes:

.18+.124+.029 = .333

Since it's a quarterly return,

.333/4 * 20640 = 1718.28

Now, how about showing some ideas on the others you posted?