Will turbotax ask me to attach supporting documentation for state tax credits like the Maine Student Loan Repayment Tax Credit (SLRTC)?

It depends on whether you have claimed the Student Loan Repayment Tax Credit (SLRTC) or Educational Opportunity Tax Credit (EOTC) in the past, or if this is your first year. 

According to the Maine Revenue Service:

"If this is the first year you are claiming the SLRTC and the documentation has not been previously provided to claim either the SLRTC or EOTC, you must include with your completed Maine individual income tax return (Form 1040ME) and Student Loan Repayment Tax Credit Worksheet:

• a complete copy of your college transcript;
• documentation that the educational loans qualify for the SLRTC; and
• documentation showing the actual student loan payments you paid directly to the lender during the tax year."

If you do need to send documentation with your state return, you will need to print, sign and mail your state return with your documentation attached.