>Yes -- once you make above the taxable threshold, the system will withhold.

OP seems to be asking once they make a certain amount in a year, will withholding start. The answer is no. Withholding is based on annualized income, so it depends on the paycheck amount × the number of pay periods. In other words, it's based on the pay rate, not the amount earned so far (otherwise, everyone would get tax free paychecks in January thanks to the standard deduction).

Like HoH with 3 kids means you need $75k to have tax liability. If OP makes say , $3,000 per biweekly paycheck (>$75k) they will have withholding from the first paycheck (as opposed to $0 withheld and then a big chunk on their last paycheck).