Otdfbt

If someone, in 2018, pays taxes, including interest and penalties, owed for tax years 2016 and 2017, then can that person claim a deduction for the paid taxes, only the original amount and no the taxes and fees, for their income for fiscal year 2018?

For example, suppose the person has gross income of $100k and owed $20k in both tax years 2016 and 2017, for a total owed taxes of $40k, but does not pay them on time. IRS imposes late penalty & interest fee of $5k until the person pays IRS total owed $45k in 2018. Person has gross income of $100k in 2018. Can the person claim $40k deduction for paying prior year federal taxes in the 2018 1040?

Any references are appreciated.

No! You can't take a tax deducton on tax*. Which is what the $40k is.

Tax isn't normally tax deductible when you pay it on time. Paying it late doesn't somehow make it more deductible.

Whether those interest and penalties are deductible is another question, but the same answer.

* You can often deduct taxes paid to other entities, such as your state or another country.

If this was allowed, why would you pay taxes on time? For simplicity suppose that over three years income was 100k each year, and tax 20%. Normally, you would pay 20k each year for a total of 60k.

Now suppose you don't pay the first two years and pay 45k on the third one, including the penalty. If you were allowed to deduct the 45k, now the tax for the third year would be 20% of 55k, so 11k. The total paid would 45k+11k=56k, so not paying taxes in time would save you money.

The above effect would be more pronounced if we consider marginal tax.

No serious government can allow that (I've seen things like that happen in some shady places, but that's precisely one of the reasons they are shady and people evade taxes).

It looks like federal back taxes are not deductible on the following year's federal tax return. I guess this makes sense since from gov's point of view they were owed to begin with so no reason to be able to deduct them.