Why is it important to line up the numbers correctly when using the standard subtraction algorithm?

Lining up the numbers correctly ensures that you are subtracting the correct place values from each other (ones from ones, tens from tens, etc.).

Subtracting Four-digit Numbers Lesson Plan for Grade 4th Grade

I can subtract four-digit numbers with regrouping.

1
The standard subtraction algorithm involves lining up two numbers with each place value aligned and subtracting, starting in the ones place.
2
It is important to put the larger number on top in subtraction to avoid negative numbers and to make borrowing easier.
3
To check your answer in subtraction, add the difference to the subtrahend; it should equal the minuend.