If you are asking how to determine how much you made during 2019, you should receive either a W2 form, if you were an employee, or a 1099 form, if you were a contractor and earned more than $599.
If you have not received these forms, and don't receive them in the next week or so, you should contact your employers and request these forms and/or an accounting of what was paid to you. (They are required to be mailed to you by January 31st)
If you had a checking account and deposited the checks/funds you received into the account, you can obtain those bank statements or request a transaction list from your bank and add up your deposits from your work.
xmasbaby0 provided the additional links to obtain copies of your W2 or tax transcripts from Social Security and IRS.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
