If statement for days with no data

Hi Jenn_Hill_13 
Try this: did it free hand, so let me know if you have any issues. Using the Index to go back 1 row.
Let me know if you have any questions.

If this solves your issues, please mark it as the solution, so that others can find it easily. Kudos 👍are nice too.
Nathaniel

BalanceCheck =

VAR _presIndex = 'tGL Combined'[Index]

VAR _prevIndex = 'tGL Combined'[Index] - 1

VAR _presCalc =
    CALCULATE (
        SUM ( 'tGL Combined'[Balance] ),
        FILTER ( 'tGL Combined', 'tGL Combined'[Index] = MAX ( 'tGL Combined'[Index] ) )
    )
VAR _prevCalc =
    CALCULATE (
        SUM ( 'tGL Combined'[Balance] ),
        FILTER ( 'tGL Combined', 'tGL Combined'[Index] = prevIndex )
    )
RETURN
    IF ( _presCalc = 0, _prevCalc, presCalc )