I live in NC and telework but physically work 48 days a year in MD. What state withholds state taxes and do i file for both states?

[Hal_Al]

Technically, you are required to file tax returns in both states, but "nobody" does. See http://money.cnn.com/2013/06/28/pf/taxes/business-traveler-tax-threat/  

Both MD and NC will tax that 48 day income, but NC will give you a credit (or partial credit) for what you pay to MD.  For most people, it comes out even and that's why they don't bother filing another return.

As to withholding, that's up to your employer.  If he withholds MD, then you will have to file an MD return. 

[TomD8]

Since you are an NC resident, ALL your income is taxable by NC, regardless of where you earn it.

Income you earn by working in MD is also taxable by MD.  Here are MD's rules for taxation of non-residents: https://taxes.marylandtaxes.gov/Individual_Taxes/Individual_Tax_Types/Income_Tax/Filing_Information/...

Therefore you must file both  a non-resident MD tax return and a home state NC return.

As @Hal_Al stated, you'll be able to take at least a partial credit on your NC return for the taxes you pay to MD, so you won't be double-taxed.

In TurboTax, be sure to complete your non-resident MD return before you work on your home state NC return, so that the credit flows properly.