Based on IRS’s instruction and links included here:

There are steps people can take now to make sure their tax filing experience goes smoothly in 2021. First, they can visit the Get Ready page on IRS.gov.

Here are a few other things people can do now:

Check their withholding and make any adjustments soon
Since most taxpayers typically only have a few pay dates left this year, checking their withholding soon is especially important. It’s even more important for those who:
  • Received a smaller refund than expected after filing their 2019 taxes this year.
  • Owed an unexpected tax bill last year.
  • Experienced personal or financial changes that might change their tax liability.

Some people may owe an unexpected tax bill when they file their 2020 tax return next year, if they didn’t have enough withheld throughout the year. To avoid this kind of surprise, taxpayers should use the Tax Withholding Estimator to perform a quick paycheck or pension income checkup. Doing so helps them decide if they need to adjust their withholding or make estimated or additional tax payments now.

Gather tax documents and keep them for at least three years
Everyone should come up with a recordkeeping system. Whether it’s electronic or paper, they should use a system to keep all important information in one place. Having all needed documents on hand before they prepare their return helps them file a complete and accurate tax return. This includes:
  • Their 2019 tax return.
  • Form W-2 from employers.
  • Form 1099 from banks and other payers.
  • Forms 1095-A from the marketplace for those claiming the premium tax credit.
  • Form 1099-NEC, Nonemployee Compensation
  • Notice 1444, Your Economic Impact Payment.

Most income is taxable, including unemployment compensation, refund interest and income from the gig economy and virtual currencies. Therefore, taxpayers should also gather any documents from these types of earnings. People should keep copies of tax returns and all supporting documents for at least three years.

Confirm mailing and email addresses
To make sure forms make it to the taxpayer on time, people should confirm now that each employer, bank and other payer has the taxpayer’s current mailing address or email address. Typically, forms start arriving by mail or are available online in January.

Remember these new things when preparing for the 2021 tax filing season
  • Taxpayers may be able to claim the recovery rebate credit if they met the eligibility requirements in 2020 and one of the following applies to them:

     – They didn’t receive an Economic Impact Payment in 2020.
     – They are single and their payment was less than $1,200.
     – They are married, filed jointly for 2018 or 2019 and their payment was less than $2,400.
     – They didn’t receive $500 for each qualifying child.

  • Taxpayers who received a federal tax refund in 2020 may have been paid interest. The IRS sent interest payments to individual taxpayers who timely filed their 2019 federal income tax returns and received refunds. Most interest payments were received separately from tax refunds. Interest payments are taxable and must be reported on 2020 federal income tax returns. In January 2021, the IRS will send a Form 1099-INT, Interest Income to anyone who received interest totaling at least $10.

根据IRS：人们现在可以采取一些措施来确保其2021年的纳税申报工作顺利进行。现在可以做以下几件事：

1. 检查其预扣并尽快进行任何调整
   由于大多数纳税人今年通常只剩下几个支付日期，因此尽快检查其预扣税就显得尤为重要。对于那些谁：
   •今年提交了2019年税款后，收到的退款比预期少。
   •去年欠了一张意外的税单。
   •经历过的个人或财务变更可能会改变其应纳税额。

如果某些人全年的预扣额不足，可能会在明年提交2020年纳税申报表时欠下意想不到的税单。为避免此类意外，纳税人应使用预扣税估算器进行快速薪水检查或养老金收入检查。这样做有助于他们确定是否需要调整预扣税或现在支付估计或额外的税款。

2. 收集税务文件并将其保存至少三年
每个人都应该提出一个记录保存系统。无论是电子的还是纸质的，他们都应该使用一种系统将所有重要信息保存在一个地方。在准备纳税申报单之前准备好所有需要的文件，有助于他们提交完整，准确的纳税申报单。这包括：
•他们的2019年纳税申报表。
•雇主的W-2表。
•银行和其他付款人的1099表。
•从市场上为要求保费税收抵免的人填写表格1095-A。
•1099-NEC表格，无雇员补偿
•1444号通知，您的经济影响付款。

大多数收入应税，包括失业补偿，退还利息以及零工经济和虚拟货币的收入。因此，纳税人还应从此类收入中收集任何文件。人们应将纳税申报表和所有证明文件的副本保存至少三年。

3. 确认邮件和电子邮件地址
为了确保表格按时到达纳税人，人们现在应该确认每个雇主，银行和其他付款人都具有纳税人当前的邮寄地址或电子邮件地址。通常，表格开始通过邮寄到达，或在一月份在线提供。

4. 在为2021年报税季做准备时，请记住这些新事
•如果纳税人符合2020年的资格要求，并且他们适用以下条件之一，则可以索取回收返利抵免：

 -他们没有在2020年收到经济影响付款。
 -他们是单身，付款少于$ 1,200。
 -他们已婚，共同于2018或2019年提交，付款少于$ 2,400。
 -他们没有为每个符合条件的孩子收取$ 500。

•在2020年收到联邦退税的纳税人可能已获得利息。国税局向个别纳税人发送了利息付款，这些纳税人及时提交了2019年联邦所得税申报表并收到了退款。大多数利息付款是与退税分开收取的。利息支付是应纳税的，必须在2020年联邦所得税申报表中报告。在2021年1月，美国国税局将向所有收到至少10美元利息的人发送1099-INT表格，利息收入。