Updated October 19, 2026. Quick answer: Boxes 4a, 4c, 5a and 5b on Form 1098-C tell you what the charity did with your vehicle and, through that, how your deduction is measured. If the charity sold the vehicle, box 4c shows the gross proceeds and the Instructions for Donor generally cap the deduction at the smaller of that amount or the vehicle’s fair market value. If box 5a or 5b is checked, the deduction generally equals fair market value on the date of the contribution.
What boxes 4a, 4c, 5a and 5b report
The charity checks one of three certifications, and the box it checks decides which deduction rule the Instructions for Donor apply. The form’s Copy B states the starting point in its margin: “Unless box 5a or 5b is checked, your deduction cannot exceed the amount in box 4c.” The identification details for the gift are on the Form 1098-C boxes 1 to 3 page, and the goods and services entries are on the Form 1098-C boxes 6a to 7 page.
Each of the four boxes is described in the donor instructions. The sections below take them in order and the table that follows collects all four with the rule each one triggers.
The four boxes at a glance
The middle column is how the donor instructions describe the box. The right-hand column is the deduction rule the same instructions attach to it.
| Box | What it means | The deduction rule it triggers |
|---|---|---|
| Box 4a: sold in an arm’s length sale | “This box is required to be checked by the charity to certify that the donated vehicle was sold for more than $500 to an unrelated party in an arm’s length transaction.” | “If box 4a is checked, you generally can take a deduction equal to the smaller of the amount in box 4c or the vehicle’s fair market value (FMV) on the date of the contribution.” |
| Box 4c: gross proceeds | “Shows the gross proceeds the charity received from the sale of the donated vehicle.” | “Unless box 5a or 5b is checked, your deduction cannot exceed the amount in box 4c.” |
| Box 5a: significant use or improvement first | “This box is required to be checked by the charity to certify that the donated vehicle will not be sold before completion of a significant intervening use or material improvement by the charity.” | “If the box is checked, you generally can take a deduction equal to the vehicle’s FMV on the date of the contribution.” |
| Box 5b: needy individual | “This box is required to be checked by the charity to certify that the donated vehicle is to be transferred to a needy individual in direct furtherance of the donee’s charitable purpose” | “If this box is checked, you generally can take a deduction equal to the vehicle’s FMV on the date of the contribution.” |
Where a box has an FMV rule, the instructions add a qualifier: “However, if that value was more than your cost or other basis, see Pub. 526, Charitable Contributions.” That sentence appears in each of the three rules, so a vehicle that was worth more than you paid for it is a case to read about in Publication 526 before you finalize anything.
Box 4a and box 4c: the charity sold the vehicle
Box 4a is the sale certification. The charity-facing instructions say it applies if the vehicle “is sold to a buyer other than a needy individual” and add that the charity must “certify that the sale was made in an arm’s length transaction between unrelated parties.”
Box 4c then reports the money. The donor instructions say “Shows the gross proceeds the charity received from the sale of the donated vehicle.” The charity is told how to figure the entry: “This is generally the sales price.” and “Do not reduce this amount by any expenses or fees.” So the number in box 4c is the gross figure, before the charity’s costs of selling.
The deduction rule for this path is: “If box 4a is checked, you generally can take a deduction equal to the smaller of the amount in box 4c or the vehicle’s fair market value (FMV) on the date of the contribution.” Box 4b, the date of sale, also matters for timing; the charity has until “30 days after the date it sold the donated vehicle (if box 4a is checked)” to furnish the form.
Box 5a: significant use or material improvement
Box 5a is for a different story. The charity does not plan to sell the vehicle right away. The donor instructions describe the certification: “This box is required to be checked by the charity to certify that the donated vehicle will not be sold before completion of a significant intervening use or material improvement by the charity.”
The charity-facing instructions define both terms. On use: “There is significant intervening use only if the organization actually uses the vehicle to substantially further the organization’s regularly conducted activities, and the use is significant, not incidental.”
On improvement: “Material improvements include major repairs and additions that improve the condition of the vehicle in a manner that significantly increases the value.” The same instructions list what does not count: “Material improvements do not include cleaning, minor repairs, routine maintenance, painting, removal of dents or scratches, cleaning or repair of upholstery, and installation of theft deterrent devices.”
When box 5a is checked, the charity also completes box 5c, which on the form reads “Donee certifies the following detailed description of material improvements or significant intervening use and duration of use”. Box 5a leads to this rule for you: “If the box is checked, you generally can take a deduction equal to the vehicle’s FMV on the date of the contribution.”
Box 5b: a needy individual
Box 5b covers a gift that goes to a person in need. The donor instructions describe it as a transfer “to a needy individual in direct furtherance of the donee’s charitable purpose of relieving the poor and distressed or underprivileged who are in need of a means of transportation.”
The charity-facing instructions add a point about the money: “Do not enter any amount in box 4c.” and “The donor’s contribution deduction for a sale for this purpose is not limited to the gross proceeds from the sale.” That is why the margin note on Copy B says the box 4c ceiling applies only unless box 5a or 5b is checked.
The donor rule for box 5b is the same as for 5a: “If this box is checked, you generally can take a deduction equal to the vehicle’s FMV on the date of the contribution.”
Where it goes on the return
Whichever box is checked, the donor instructions point to the same attachments for a larger gift. They say “Generally, you must also attach Form 8283, Noncash Charitable Contributions, if the amount you deduct for all noncash gifts is more than $500.” Walk through the form on the Form 8283 page. For the way donations of property appear on Schedule A, see the page on gifts other than cash or check on Schedule A, and for the broader rules see charitable giving.
Edition and box numbers
This page reads Form 1098-C (Rev. April 2025), the edition printed in the header of the form, together with the charity-facing Instructions for Form 1098-C, which are dated Rev. November 2019. The charity-facing instructions explain: “Form 1098-C and these instructions have been converted from an annual revision to continuous use.” “Both the form and instructions will be updated as needed.” Check the year and edition printed on the form you received, because box numbers can change between editions.
Common mistakes
- Using the box 4c figure when box 5a or 5b is checked. The Copy B note says “Unless box 5a or 5b is checked, your deduction cannot exceed the amount in box 4c.”
- Skipping the cost check. For all three rules the donor instructions say “However, if that value was more than your cost or other basis, see Pub. 526”.
- Treating box 4c as a net figure. The charity is instructed “Do not reduce this amount by any expenses or fees.”
Related: Form 8283, charitable giving, and gifts other than cash or check on Schedule A.
Sources
- Form 1098-C, Contributions of Motor Vehicles, Boats, and Airplanes, with Instructions for Donor: https://www.irs.gov/pub/irs-pdf/f1098c.pdf
- Instructions for Form 1098-C: https://www.irs.gov/pub/irs-pdf/i1098c.pdf
- IRS: About Form 1098-C: https://www.irs.gov/forms-pubs/about-form-1098-c
Read from the IRS documents linked above on October 19, 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.