Start with the number on the right. Check to ensure the top numbers are bigger than the bottom numbers. If the numbers are larger on the bottom, you will need to regroup. Go to Section 2: Subtraction with Regrouping. If all numbers on top are larger than the numbers directly below, then no regrouping is needed.
Begin with the numbers on the right. Take away the bottom number from the top number. Example 5 (top) - 3 (bottom) = 2. Continue across your problem from right to left.
Check your work by adding your answer to the number subtracted (bottom). If your answer is correct, it will add up to the original number found on the top of the original problem.
Check your top numbers, starting with the numbers on the right. If the numbers on the bottom are smaller than the top, go to Section 1: Subtraction without Regrouping. If the numbers on top are smaller than the number on the bottom, you will need to regroup. It is important to note that not all numbers will need regrouping.
Start with the ones column (far right). If the number on top is smaller than the number on the bottom, you will need to borrow. To borrow, look at the number directly to the left of the ones (in the tens place). You will reduce this number by one digit. Example: If the number in the tens place is 5 it becomes 4. Borrowing adds 10 ones to the number in the ones column. If your number in the ones column is 3, it becomes 13.
If no regrouping is needed, subtract as usual and move to the next column.
Look at the tens column. If you borrowed, look at the new (smaller) number, is it smaller than the number on the bottom? If so, you will borrow from the next column to the left as you did in step 2. If no borrowing is needed, subtract as you would normally.
Add your answer to the number you subtracted to check your work. It will add up to the original number if correct. If it does not, check to make sure you borrowed correctly, reducing numbers you borrowed from. Make sure you subtracted from the top down.