Yes. Even though you are required to start drawing down the account, you can continue to add to it through deductible contributions as long as you have net earnings from self-employment. However, you can no longer contribute to a traditional IRA if you had otherwise been able to do so; no contribution is allowed for the year in which you turn age 70-1/2 or any later year. There is no age limit for making Roth IRA contributions as long as you continue to have earned income.
Total business receipts reported on Schedule C or Schedule C-EZ before deducting adjustments for returns and allowances and cost of goods sold.