Get your taxes done using TurboTax

@Critter-3 Thank you for all this information! I had forgotten about the Safe Harbor rules - looks like they apply at the Federal AND state levels. 

My income across all sources has always been more than $150K...and will likely continue that way.

This is what I could find for the safe harbor percentage (for the prior tax year) for:

• Federal - 110% of last year's tax, according https://turbotax.intuit.com/tax-tips/small-business-taxes/estimated-taxes-how-to-determine-what-to-p... 
• State of NC - I couldn't find this. Is it 110% of last year's tax? Found that from here but it's not official + looks really out of date (2009): https://www.tjtpa.com/wp-content/uploads/200908.pdf ?
• State of CA - 110% of last year's tax, according to https://www.ftb.ca.gov/pay/estimated-tax-payments.html 
• State of NY - 110% of last year's tax, according to https://www.tax.ny.gov/pit/estimated_tax/who_must_make.htm

I am mostly concerned about the State of NC (my home state of residence). Are you able to find an official source mentioning the safe harbor rules? I couldn't find it at https://www.ncdor.gov/taxes-forms/individual-income-tax/estimated-income-tax

Thank you.