When you type numbers that begin with zeros, like in some personal identification numbers, phone numbers, credit card numbers, product codes, or postal codes, Excel removes these leading zeros. To prevent this, you can first apply the Text format to the cells before you type or paste the numbers. Here’s how:
Select the cells on your worksheet where you’ll be adding the data.
On the Home tab, click Number Format >Text.
Type or paste the numbers in the formatted cells.
Tip: Also apply Number format for numbers that are 12 digits or more otherwise Excel Online automatically applies the Scientific format and converts any numbers after the 15th digit to zeros.