For a Maryland non resident, the questions wants to enter the amount of child care that incurred outside Maryland? If I worked in Maryland is that 100 percent?

Since you have income outside of MD the amount of childcare paid "Outside" of MD is the proportion of childcare costs that is the same proportion of income earned outside of MD / total income (FED Adj Gross Income).  For example, non-MD income was 5000 and total income was 10,000.  The proportion is .5 or 1/2.  So .5 times childcare costs paid (up to a maximum $3000 or $6000 as applicable) will yield the outside MD portion.  

Here is an extract from the MD form 505 instructions for subtractions from MD income.

"To the extent that one or more of these items apply to your Maryland income, include only that part attributable to Maryland on the appropriate line in Part II of Form 505SU. Unless a different method more accurately attributes the subtraction to Maryland, the part attributable to Maryland is calculated by multiplying the amount by a fraction the numerator of which is your Maryland adjusted gross income from line 17 column 2, and the denominator of which is federal adjusted gross income from Line 17, column 

1. f. Child and dependent care expenses. You may subtract the cost of caring for your dependents while you work. There is a limitation of $3,000 ($6,000 if two or more dependents receive care). To claim this subtraction from income, enter the smaller of (a) the amount on line 6 of federal Form 2441 or (b) $3,000 ($6,000 if two or more dependents receive care)."

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[Edited 2/12/2024 9:23AM PST]