As a self-employed worker, do you pay taxes quarterly or annually?

Assuming you are talking about income taxes, I am trying to figure out why you think it is optional.

Well, ok, technically it is optional I guess if you like paying penalties an interest in addition to the income tax you owe.

The only time you do not have to file quarterly estimated taxes is if you had a zero tax due last year.

The IRS is specific, if you will owe more than $1,000 in taxes, you use estimated quarterly taxes.

Individuals, including sole proprietors, partners, and S corporation shareholders, generally have to make estimated tax payments if they expect to owe tax of $1,000 or more when their return is filed.

If you didn’t pay enough tax throughout the year, either through withholding or by making estimated tax payments, you may have to pay a penalty for underpayment of estimated tax. Generally, most taxpayers will avoid this penalty if they owe less than $1,000 in tax after subtracting their withholdings and credits, or if they paid at least 90% of the tax for the current year, or 100% of the tax shown on the return for the prior year, whichever is smaller.
https://www.irs.gov/businesses/small-businesses-self-employed/estimated-taxes