Is it true that only 85% of your SSA income is taxable? If it is do I reduce what I report by 15%

[TomK]

Not quite.  A quick way to find out if any of your benefits may be taxable is to add one-half of your Social Security benefits to all your other income, including any tax-exempt interest. Next, compare this total to the base amounts below. If your total is more than the base amount for your filing status, then some of your benefits may be taxable. The three base amounts are:

• $25,000 - for single, head of household, qualifying widow or widower with a dependent child or married individuals filing separately who did not live with their spouse at any time during the year
• $32,000 - for married couples filing jointly
• $0 - for married persons filing separately who lived together at any time during the year

Depending on your income and filing status, up to 85% of your Social Security benefit can be taxable:

• If you're single, a combined income between $25,000 and $34,000 means that up to 50% of your benefits could be taxable. A combined income greater than $34,000 means that up to 85% of your benefits could be taxable. Of course, if your combined income is less than $25,000, none of your Social Security benefits are subject to tax, as I discussed in the previous section.
• If you're married and file a joint tax return, then a combined income between $32,000 and $44,000 puts you in the 50% taxable range, and income over $44,000 means that up to 85% of your benefits are taxable.
• If you're married and file separately, up to 85% of your benefits can be taxed, regardless of your income.

Notice that I said "up to" 50% or 85% of your benefits is taxable. It's not a simple of multiplication, and there are several variables that determine the actual amount of taxable Social Security benefits.

https://ttlc.intuit.com/replies/3299920

[ajrubins]

I have read that depending on your income and a number of factors, you could have 50% of your total Social Security Income taxed, or it could be as high as 85% taxed.  Is it a sliding scale such that it could be a percentage between 50% and 85%?     If I look at my 1040-SR that TurboTax created for me and divide box 6b by box 6a, I come out to a little over 55%.   Can that be correct?

[LeonardS]

Yes, the taxable amount of your social security income is on a sliding basis,  Once you have exceeded the threshold the taxable amount starts at 50% and can reach a maximum of 85%

According to the IRS, the quick way to see if you will pay taxes on your Social Security income is to take one-half of your Social Security benefits and add that amount to all your other income, including tax-exempt interest.

For single people, your Social Security benefits aren't taxed if your provisional income is less than $25,000. The threshold is $32,000 if you're married and filing a joint return. If your provisional income is between $25,000 and $34,000 for a single filer, or from $32,000 to $44,000 for a joint filer, then up to 50% of your Social Security benefits may be taxable. If your provisional income is more than $34,000 on a single return, or $44,000 on a joint return, up to 85% of your benefits may be taxable.

@ajrubins