Which specific lines on Form 1040 should taxpayers check to compute AGI before applying the senior bonus MAGI add‑backs?
Executive summary
Taxpayers should begin MAGI work by reading their Adjusted Gross Income (AGI), which is shown on Line 11 of Form 1040; that figure is the baseline before any “senior bonus” or other MAGI add‑backs are applied [1] [2]. Beyond Line 11, specific 1040 lines that commonly matter for MAGI calculations include Social Security amounts (lines 6a/6b) and entries for IRA conversions or rollovers (lines 4b and 5b), and taxpayers must remember that the precise add‑backs for a “senior bonus” follow the statutory definition for that deduction and can differ from other MAGI definitions [2] [3] [4].
1. Start where the IRS tells taxpayers to start — Line 11 is AGI
The Internal Revenue Service explicitly identifies AGI on Form 1040 as the number shown on Line 11, and every MAGI calculation begins with that figure; authoritative IRS guidance directs taxpayers to “start with your AGI (Line 11 on Form 1040, 1040‑SR, or 1040‑NR)” when determining modified adjusted gross income for eligibility tests [2] [1].
2. Check 1040 lines that commonly feed MAGI add‑backs (what to look for on the form)
Although AGI is Line 11, MAGI requires adding back certain items that may appear elsewhere on the return: nontaxable Social Security components are calculated from lines 6a and 6b (the IRS cites “Form 1040 or 1040‑SR line 6a minus line 6b” as a MAGI consideration), and conversions from traditional IRAs to Roth IRAs appear on line 4b while rollovers to Roth IRAs appear on line 5b — all of which the IRS flags as potential add‑backs when computing MAGI for specific benefits [2].
3. Remember the adjustments column — the deductions that produced AGI are summarized before Line 11
Line 11 is the result of gross income less the “above‑the‑line” adjustments that appear in the return’s adjustments area (for example, those cumulative adjustments are reflected on line 10 and feed into line 11), so anyone reconciling AGI to MAGI should review the adjustments that produced Line 11 because many MAGI definitions require adding some of those adjustments back to AGI [1] [3].
4. The “senior bonus” MAGI add‑backs are specific — foreign exclusions and similar items are often added back
When journalists and advisors discuss the new “senior” deduction, coverage and guidance advise starting with AGI on Line 11 and then adding particular exclusions back in — for example, the foreign earned income exclusion, foreign housing exclusion and amounts excluded because they were received from Puerto Rico or American Samoa are explicitly called out as add‑backs for that new MAGI test [4]. That demonstrates the central point: the list of add‑backs is not generic and depends on the statute or benefit being tested [4] [5].
5. Practical takeaway: inspect Line 11, then the lines that document the special items
For practical accuracy, pull Line 11 as the baseline, then inspect lines that document commonly added‑back items — Social Security (6a/6b), IRA conversions (4b), rollovers to Roths (5b), and the adjustments entries that comprise Line 11 (e.g., line 10 and related schedules) — because MAGI is not printed on the 1040 and must be reconstructed by adding back the statutorily specified items [2] [1] [3] [6].
6. Caveats, competing sources, and where to confirm
Tax‑prep firms and financial outlets repeat the same practical advice — Line 11 is the starting point and add‑backs vary by benefit — but commercial guides differ slightly in which specific deductions they emphasize (IRA contributions, student‑loan interest, HSA contributions, etc.), underlining that MAGI’s precise composition is context‑dependent and taxpayers should consult the IRS instructions or benefit‑specific worksheets for the senior deduction to confirm which add‑backs apply to their case [3] [5] [7]. The IRS also offers calculators and instructions tied to particular credits or deductions to avoid misapplication [2].