Later this month more than 39 million households are set to receive advance payments of the Child Tax Credit (CTC) that was expanded in the March 2021 American Rescue Plan. Many households are uncertain about how the advance payments will affect their refunds or taxes owed when they file next year, and some questions about specific taxpayer situations have yet to be answered by the Internal Revenue Service (IRS).

The American Rescue Plan temporarily expanded the Child Tax Credit for tax year 2021 from its current $2,000 maximum to $3,600 for children under age 6 and $3,000 for children age 6 to 17. For one year only, the credit no longer phases in with income but is instead fully refundable. Half of the expanded amount will be paid out in monthly installments to eligible households, meaning they do not have to wait until they file taxes to receive some of the Child Tax Credit benefits.

The extra amount of the credit—$1,600 for younger children, $1,000 for older children—phases out at $50 for every $1,000 in income earned over $112,500 for head of household filers and $150,000 for joint filers until the credit reaches what beneficiaries would receive under prior law. That means no one will see tax increases relative to prior law as the extra credit amount phases out.

While there are no tax increases, some households may experience surprises when they file their taxes next year. A dollar of Child Tax Credit received in advance is a dollar less received at filing time. While some households may prefer receiving their Child Tax Credit earlier, it is important they are fully aware of the trade-offs.

For example, consider a married filing jointly household with a 10-year-old child. Prior to the expansion, let’s assume they received a $2,000 Child Tax Credit at filing time, and had adjusted their paycheck withholding to receive the entire $2,000 as a refund. Under the expanded Child Tax Credit, they are now eligible for a $3,000 credit—$1,500 to be received in advance monthly payments of $250 starting this July.

Keeping everything else the same, if the household makes no adjustments to their withholding, when they file their taxes next year they may only receive $1,500 of Child Tax Credit at filing time. That is $500 less at tax time even though they received $1,000 more than the previous year when including the advanced payments.

The situation may be even more complicated for other households. For example, some filers with children have split custody arrangements, in which separated parents take turns claiming the Child Tax Credit from year to year. The IRS has not yet provided guidance for how such situations will be handled even as the opt out date for the first payment has passed, but it is likely that the advanced payment will be sent to the parent who claimed the credit on the most recent tax return—meaning one parent may receive the credit two years in a row.

And for taxpayers whose income or family situation has changed since they last filed taxes, they will not be able to provide updated information to the IRS until September, when a new tool will be available on the IRS website.

If the advance monthly payments a taxpayer receives exceed the amount of Child Tax Credit they are eligible for, they may need to repay the excess when they file their taxes next year. The American Rescue Plan did allow for a safe harbor “repayment protection” for certain taxpayers. Joint filers with under $60,000 in modified adjusted gross income (MAGI), head of household filers under $50,000, and single filers under $40,000 whose main home was in the U.S. for more than half the year would be protected from repaying $2,000 per “excess qualifying child.”

For example, suppose the IRS calculated advanced payments for a joint filer with $40,000 in income based on their previous tax return that correctly claimed three qualifying children, but when they file taxes next year, they will only claim two children. In that case, the filer would receive $2,000 in repayment protection for their one excess qualifying child. The repayment protection phases out for taxpayers with income above the specified thresholds.

For taxpayers who do not want to receive their payment in advance, the IRS has provided a portal that allows taxpayers to opt out—but the deadline to make that choice has already passed for the first payment. It is important to note that both spouses must opt out of receiving the advance payments. If only one joint filer opts out, that choice only applies to that filer’s share of the advance payment and not their spouse’s share.

Amidst the outstanding questions, potential confusion over how advanced payments will affect tax refunds, and an incomplete portal to update taxpayer information, the IRS will begin sending payments to millions of households this month. It is important that taxpayers fully understand the trade-offs of receiving their refundable Child Tax Credit in advance to avoid surprises next year. It will also be important for policymakers to closely monitor the administration of advance payments and evaluate the experience before deciding to extend, or make permanent, the policy.