Why do i owe in my 2020 tax return? I started a new job in 2020 and used a 2020 w4. I have no dependents, single. simple w4.

Did you have any other type of income in 2020, such as Unemployment Comp?  It's taxable, but you may not have had enough withheld from it.

thanks for the reply. I was NOT collecting in 2019/2020 after i left my job. 

Check all your data entry for any typos, especially commas, decimal points and extra zeroes. 

i checked my data before i submitted.