The letter tells you exactly why you owe the money.  What are they saying caused the increase in tax?

it shows 0 taxable wages and -$12,131 on line 43 0 tax on line 44 and o tax on line 63. I need you resend the 2016 filing. I received a refund of $2,800 that year.

it shows 0 taxable wages and -$12,131 on line for taxable income on line 43, 6 tax on line 44, and 0 tax on line 63. I need you to resend the 2016 filing. I received a refund of $2,800 that year. I don't know why they have the wrong information.

You'll have to call the IRS and ask them why they changed your tax return so drastically .

call to make sure you're not looking at a scam letter.

What you are saying about the numbers on those lines doesn't seem to lead to a $7,000 billing for tax, or maybe  you're entering amount son your own tax return and not the letter they sent explaining their changes.

You should call this group for help with your notice.  We do not resend returns for you but someone here can help you resend your own return.