Where do I show that all income for the year was earned in one quarter (prior to Covid)?

[xmasbaby0]

Why do you think you need to show that?   You are filing a 2020 tax return to show your income for the tax year.   Your tax return is not going to break your yearly income down by quarters.

[kristentaeger]

I thought I saw a question asking if income was earned only during

part of the year.

[beyondmom]

I don't know why he asked it, but I know there was a time when income that was significantly higher in only one quarter meant that your tax rates were calculated differently.  That may no longer be the case.  It was a long time ago that I last went looking for the same answer.  We wound up back pay from a union contract settlement that threw us into a different tax bracket, but wouldn't have if it were being calculated separately from the other quarters (which is what used to happen.)

[Critter-3]

Calculating quarterly income is used when you annualize it for the underpayment penalty on form 2210. 

[VolvoGirl]

See form 2210

If you do not pay enough tax, you may have to pay a penalty for underpayment of estimated tax. Even if you are getting a refund you can still owe a penalty for not paying in evenly during the year.  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. It is included in your tax due or reduces your refund.

You might be able to eliminate it or at least reduce it.  You can go to Federal Taxes tab or Personal tab, under Other Tax Situations and select Start by the Underpayment Penalties. You will answer a series of questions that may reduce or eliminate the penalty. Or you can elect to have the IRS figure the penalty for you.  It's form 2210.

It's under

Federal or Personal (for Home & Business Desktop)

Other Tax Situations

Additional Tax Payments

Underpayment Penalties - Click the Start or update button

If you have the desktop program you can switch to Forms Mode (click forms in the upper right (left for Mac)) and open the 2210 form.  If the 2210 doesn't show up in the left column, click on Open Forms at the top of the left column.  Type 2210 in the search box and open the 2210 form.  Check box C to let the IRS calculate it.