Your child learns to add and subtract numbers of up to four digits by lining them up in columns, ones under ones, tens under tens, and so on, and working from right to left.
In Year 4, children use the column method to add and subtract whole numbers with up to four digits. They write the numbers one under the other, keeping each place value in its own column, and carry or exchange when a column does not have enough. The curriculum asks for these formal written methods "where appropriate", so children are also expected to judge when a written method is the sensible choice.
A common mistake is misaligning the columns, for example writing 1,246 and 58 so that the 8 sits under the 2 instead of the 6. The sum then adds the wrong digits together and gives an answer that looks plausible. In subtraction, a frequent error is taking the smaller digit from the larger one in each column regardless of which is on top, or getting stuck when a zero sits in the middle of the number, as in 4,003 minus 1,378. Borrowing across zeros is a specific step that needs practice of its own.
Printable tasks for this skill include "Add using the column method" and "Subtract using the column method", where the child works through each sum on paper. "Column addition: choose the result" and "Column addition: true or false" ask the child to check or select answers, which helps them spot misaligned columns. "Written subtraction: borrowing across zeros" targets the zero-exchange step, and "Written subtraction: true or false" gives practice in checking whether a given answer is correct.