You cannot file 2016 and 2017 together. You need to do 2017 before the tax filing deadline this year or file an extension.
You need to do 2016 as soon as possible. For information on how to do that, see below.
It's never too late to file your back tax returns.
Step 1: Gather your tax documents
To file your back tax returns, you will need the W-2s or 1099 forms you received for those tax years to report your income. If you are eligible for deductions and credits, you must also gather any receipts or other supporting records that prove your eligibility to claim them.
Step 2: Request missing documentation
If you are missing any of your tax documents from the last 10 years, you can request a copy from the IRS by filing Form 4506-T, Request for Transcript of Tax Return. Use this form only to request W-2s, 1099s and even 1098s that may provide support for some of your deductions.
Though you will not receive a duplicate of the original form, the IRS will provide you with a transcript of all relevant information, which is sufficient for filing your back tax returns. It can take the IRS up to 45 days to process your request.
Step 3: Download prior year IRS tax forms
You must always file your back tax returns on the original forms for each tax year you are filing. You can always search through the IRS website for the forms, but for quicker access, you should use sophisticated tax preparation software, such as TurboTax.
Step 4: Prepare your back tax returns
You cannot complete prior year tax forms using instructions from the current tax year. When you have all your documents in front of you and you are ready to start inputting your data, double check to make sure that the instructions you are using are for the same tax year as the tax return you are preparing. The tax law changes every year, and using the wrong instructions may require you to prepare the return over again.
Step 5: Submit your forms
Submit the forms to the IRS at the address listed in the Form 1040 instructions. If you owe additional income tax for any of the prior years, remember to include as large of a payment as you can to reduce your interest charges. Unlike tax penalties which stop accruing when the maximum is reached, monthly interest still accrues indefinitely until the tax is paid. Once the IRS receives your tax returns, you should expect to receive notice of the exact penalty and interest charges you are responsible for.
