After an exhaustive search for the total number of filings for 2016 US tax filers represented under the ADA the information requested is determined to not be available in the public domain. However, it is possible to estimate, using additional data, the number of individual tax filings by disabled tax payers in 2016 was between 23,291,955 and 54,043,425.
The total 2016 US population ages 18-64 is 191,800,000 + 10,560,000 = 202,360,000 (please note that I assumed an even distribution for each age 15-19).
Total 2016 disabled population:
10.5% of 18-64 population = .105 * 202,360,000 = 21,247,800
35.4% of 65+ population = .354 * 48,480,000 = 17,161,920
21,247,800 + 17,161,920 = 38,409,720
(38,409,720/(202,360,000+48,480,000))*100 = 15.3%
Thus, 15.3% of US adults ages 18 and up are disabled.
I then picked up the number of individual returns filed in 2017 (note my assumption is that all returns filed in 2017 were for 2016 tax year. This will include any late filing and filings from prior years, which would likely be minimal).
Disabled proportion = 15.3% of this (as calculated above) =
.153 * 152,235,000 = 23,291,955 returns filed by disabled taxpayers.
We can also estimate the proportion using percentage of disabled work force:
.355 * 152,235,000 = 54,043,425 returns filed by disabled taxpayers. However, this number is likely understated because a large share of disabled taxpayers are likely not part of the workforce.
We can only estimate the exact number of disabled people filing an individual tax claim in the US as this data has not been made available. All information gathered for this request has been filled in on the attached document as requested.