The IRS wants to collect tax from you at approximately the same time you receive your income. If they don't get it then, they charge you a penalty for having to wait for it.
If you are a regular employee, your employer withholds tax from every paycheck and send it to the IRS.
Taxes are rarely withheld from 1099-MISC and 1099-NEC income. The IRS expects you, the recipient of that income, to make estimated tax payments throughout the year so you don't owe tax at the end of the year - and they don't have to wait all year for their money.
If you didn't make estimated payments during the time you received the income and end up owing tax in it, then you will be charged an underpayment penalty.
