Updated October 18, 2026. Quick answer: Lines 21 to 26 are Part II-B, a second way to measure the additional child tax credit for certain filers with three or more qualifying children and for bona fide residents of Puerto Rico. Line 21 is the social security and Medicare tax withheld from your Forms W-2, lines 22 to 25 net that against other taxes and credits, and line 26 takes the larger of line 20 or line 25.
IRS worksheets read line by line: Schedule 8812 Credit Limit Worksheet B.
Who uses Part II-B
The part is headed “Part II-B Certain Filers Who Have Three or More Qualifying Children and Bona Fide Residents of Puerto Rico”. You reach it only when the routing note after line 20 sends you here. That note is covered on the lines 15 to 20 page. If the note tells you to skip the part, you go straight to line 27.
Line 21: withheld social security and Medicare tax
The form’s caption starts “Withheld social security, Medicare, and Additional Medicare taxes from Form(s) W-2, boxes 4 and 6.” It continues “If married filing jointly, include your spouse’s amounts with yours.” It also warns “If your employer withheld or you paid Additional Medicare Tax or tier 1 RRTA taxes, or if you are a bona fide resident of Puerto Rico, see instructions”.
The instructions repeat the pointer to the extra worksheet: “If you are completing Part II-B and your employer withheld or you paid Additional Medicare Tax or tier 1 RRTA tax, use the Additional Medicare Tax and RRTA Tax Worksheet, later, to figure the amount to enter on line 21.” That worksheet is a table in the instructions, so use it there. The instructions add where the withholding is shown: “Withheld social security, Medicare, and Additional Medicare taxes should be shown on Form(s) W-2, boxes 4 and 6, and Puerto Rico Form(s) 499R-2/W-2PR, boxes 21 and 23.” Extra Medicare tax is explained on the Additional Medicare Tax page.
For Puerto Rico residents the instructions say “On line 21, include all your withheld social security, Medicare, and Additional Medicare taxes, including those taxes withheld by Puerto Rican employers that are shown on Puerto Rico Form(s) 499R-2/W-2PR.”
Lines 22 and 23: other taxes, then the total
Line 22 reads “Enter the total of the amounts from Schedule 1 (Form 1040), line 15; Schedule 2 (Form 1040), line 5; Schedule 2 (Form 1040), line 6; and Schedule 2 (Form 1040), line 13”. Those schedule lines are covered on the Schedule 2 lines 5 to 7 page and the Schedule 2 page. Line 23 is plain addition: “Add lines 21 and 22”. The instructions have no separate paragraph for lines 22 or 23.
Lines 24 and 25: what gets taken off
Line 24 differs by form. For Form 1040 and 1040-SR the caption is “Enter the total of the amounts from Form 1040 or 1040-SR, line 27a, and Schedule 3 (Form 1040), line 11.” For Form 1040-NR it is “Enter the amount from Schedule 3 (Form 1040), line 11.” The Schedule 3 line is explained on the Schedule 3 line 11 page. Line 25 then reads “Subtract line 24 from line 23.” and the form’s own caption continues with an instruction for a zero or negative result, which you should read on the form itself.
Line 26: the larger-of test
Line 26 says “Enter the larger of line 20 or line 25”. Below it the form says “Next, enter the smaller of line 17 or line 26 on line 27.” Line 17 is the cap from Part II-A, so line 27 can never exceed it.
Computed illustration, not an IRS example: if line 20 is $1,500 and line 25 is $2,100 then line 26 is $2,100. If line 17 is $1,700 then line 27 is the smaller of $1,700 and $2,100 and that is $1,700.
Where the number comes from
Line 21 comes from Forms W-2 boxes 4 and 6, Puerto Rico Forms 499R-2/W-2PR and the Additional Medicare Tax and RRTA Tax Worksheet when it applies. Lines 22 and 24 come from the schedule lines the form names. Line 23 and line 25 are arithmetic, and line 26 compares line 20 from Part II-A with line 25.
Where it goes next
Line 26 has one destination, line 27, reached by the instruction “Next, enter the smaller of line 17 or line 26 on line 27.” The result then flows to Form 1040 line 28 as explained on the line 27 page.
Edition and line numbers
This page reads the 2025 Schedule 8812 (Form 1040), Credits for Qualifying Children and Other Dependents and its 2025 instructions, the current files irs.gov served on 2026-10-18. They are the files for the tax year 2025 return, filed in 2026. The form header says “Attach to Form 1040, 1040-SR, or 1040-NR.” Check the tax year printed on the form you are filling in and use the line numbers on that year’s form, because a different year’s form can number or word its lines differently. The whole schedule is walked through on the Schedule 8812 line by line guide page.
Common mistakes
- Leaving out a spouse on a joint return. The form says “If married filing jointly, include your spouse’s amounts with yours.”
- Skipping the extra worksheet. The instructions say “use the Additional Medicare Tax and RRTA Tax Worksheet, later, to figure the amount to enter on line 21.”
- Entering line 26 on line 27 without comparing to line 17. The form says “Next, enter the smaller of line 17 or line 26 on line 27.”
Related: Additional Medicare Tax, Schedule 2, Schedule 3 line 11, and Schedule 2 lines 5 to 7.
Sources
- Instructions for Schedule 8812 (Form 1040), Credits for Qualifying Children and Other Dependents (2025): https://www.irs.gov/pub/irs-pdf/i1040s8.pdf
- Schedule 8812 (Form 1040), Credits for Qualifying Children and Other Dependents (2025): https://www.irs.gov/pub/irs-pdf/f1040s8.pdf
Read from the IRS documents linked above on October 18, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.