The Fiscal Year 2020 deficit was $3,132 billion

Total revenue for FY2020 was $3,420 billion and total expenditures were $6,552 billion.  See the September 2020 Monthly Treasury Statement. Compare these to FY2019 revenue of $3,462 billion and expenditures of $4,447 billion.  For only the month of September 2020, revenue was $373 billion (compared to $374 billion in Sept 2019) and outlays were $498 billion (compared to $291 billion in Sept 2019).

What was the biggest change from 2019?  The 2020 results were actually pretty similar to 2019, with the exception of April, May, and June.  The expenditures were fairly similar, adjusted for inflation, except for these major areas:

• Dept of Labor: $477 billion in 2020 vs $36 billion in 2019.  This was for unemployment compensation. 
• Dept of Health and Human Services: $1,504 billion in 2020 v $1,204 bn 2019.
• Dept of Education: $204 bn v $104 bn
• Dept of Treasury - Other: $629 bn vs $117 bn.  I think this was for the stimulus payments.
• Small Business Administration: $577 bn vs $456 million.  This was for PPP loans.

So I see 3 major areas of stimulus that show up on the financial statement: 1) Unemployment compensation ($441 bn more than 2019), Treasury ($512 bn more than 2019), and SBA ($577 bn more).  So a total stimulus of $1,530.  So everything else being equal, the 2021 budget would show a deficit of about $1.6 billion, without any stimulus.  Add in a $2 trillion stimulus bill (and it could be a lot more than that) and you are looking at a $3.6 billion deficit in 2021.