To subtract decimals, stack both numbers so the decimal point is in the same position, and add zeros to the right of the number with fewer digits. Subtract as though they are whole numbers. The decimal point in the answer number goes directly under those in the subtraction problem.
Lining up the decimal point ensures that each digit in the bottom number gets subtracted from the digit with the same place value in the top number's digits. The number in the 10s place in the bottom number must be subtracted from the 10s-place digit in the top number.
For numbers with nothing to the left of the decimal point, such as .145, add a zero to the left as a placeholder. Even when not doing this in the calculation steps, it is standard to add a zero on the left for the answer in laboratory notes and published work. Examples are "0.39598 milligrams" and "$0.27."