If I purchase an IRA, where do I enter this info on Turbo Tax? Will turbo tax tell me the max I am allowed to purchase?

For 2018, your total contributions to all of your traditional and Roth IRAs cannot be more than:

1. $5,500 ($6,500 if you’re age 50 or older), or
2. your taxable compensation for the year, if your compensation was less than this dollar limit.

Contributions to the Traditional IRA contributions may be tax-deductible. The deduction may be limited if you or your spouse is covered by a retirement plan at work and your income exceeds certain levels. Please see: IRA deduction limits

Roth IRA contribution might be limited based on your filing status and income. Please see 2018 - Amount of Roth IRA Contributions You Can Make for 2018

Please see the instructions below how to enter IRA contributions:

1. Login to your TurboTax Account 
2. Click "Take Me To My Return"
3. Click "Federal" from the left side of your screen
4. Click “Deductions &Credits” on the top
5. Scroll down to “Retirement and Investments” and click “Show more”
6. Scroll down to “Traditional and Roth IRA Contributions” and click “Start”