For example, if you wish to calculate a monthly average number of hours worked and use six months of data, divide the total hours your employee works in six months and divide the result by six to determine the monthly average hours of work for the employee.
Social Security disability payments may be includable in taxable income and still not increase the tax you pay. A lump-sum retroactive payment of Social Security Disability Insurance (SSDI) may be includable in taxable income, depending on the amount and your other income and deductions.
If disability benefits are your only source of income, you'll almost certainly not owe any federal income tax. But if you're filing as an individual with provisional income between $25,000 and $34,000, up to 50% of your disability benefits are considered taxable income.