Co-Writing a Book on KDP: Who Gets Paid and How to Split It
When two people write a book, the royalties land in the KDP account that published it, and dividing them is up to the partners. The questions co-authors and illustrators run into, answered with worked numbers.
Published October 17, 2026. Figures are calculated from KDP's published rates when the page is built.
Co-writing on KDP turns into bookkeeping the moment the first payment arrives, because the money comes in at one place and has to go out to two or more people. The partners and sales below are invented. The splits are worked the same way as in the royalty split calculator, which also produces each row of a running ledger: shared costs are repaid first, then the rest is divided by agreed shares.
Who does KDP actually pay?
The account that published the book. A book is set up on one KDP Bookshelf, and its royalties are paid by the payment method chosen in that account; KDP's Kindle Unlimited royalty page, for example, says page-read earnings follow "the same payment schedule and payment method you selected for your other KDP sales." Nothing in KDP's royalty pages describes dividing a payment between people, so the account holder pays everyone else. That makes the account holder the treasurer of the partnership whether they want the job or not, so decide who it is before you upload anything, and make sure the other partners can see the sales reports every month, for example as a downloaded copy of the KDP report.
If you publish several books together, the same account should usually hold all of them. Splitting a series across two accounts means two sets of reports to reconcile every month.
Do we split the list price or the royalty?
The royalty. It sounds obvious, but agreements that say "60% of sales" invite the wrong reading. A $4.99 ebook on Amazon.com with a 1 MB file earns $3.39 on the 70% option after KDP's delivery cost. Split 60/40, that is $2.03 and $1.36 per copy.
Split the $4.99 list price 60/40 instead and you get $2.99 and $2.00, which adds up to more than the $3.39 the account holder actually received. Write "of royalties received from KDP" into the agreement, and the problem goes away. It also keeps working when the price changes: put the same ebook on sale at $1.99, below the $2.99 minimum for 70% on Amazon.com, and each copy earns $0.70 at 35%, split $0.42 and $0.28. A price cut one partner wants costs the other partner money too, which is why price decisions belong in the agreement. The same applies to paperbacks, where KDP deducts the printing cost to arrive at the royalty; the paperback royalty calculator shows what's left per copy.
One of us paid for the cover. When do they get it back?
Repaying costs before anything is split is the simplest arrangement to track, but it helps to see what it does to the early months. Ana and Ben co-write a novel and agree to split royalties 50/50 after costs. Ana paid $650.00 for the cover and editing; Ben paid $250.00 for proofreading and launch ads. Each payment repays both of them in proportion to what they're owed until the $900.00 is cleared:
| Month | Royalty | To Ana | To Ben | Costs still owed |
|---|---|---|---|---|
| 1 | $220.00 | $158.89 | $61.11 | $680.00 |
| 2 | $380.00 | $274.44 | $105.56 | $300.00 |
| 3 | $510.00 | $321.67 | $188.33 | $0.00 |
| 4 | $640.00 | $320.00 | $320.00 | $0.00 |
For the first two months nothing is split at all; every dollar goes to repaying costs. In month 3 the costs are cleared and the remainder is split, and from then on each payment is shared evenly. Keeping a running "still owed" column like this one is what stops arguments later, because both partners can see exactly when the split begins.
If your costs are bigger than a few months of royalties, the break-even calculator estimates how many copies, and how many months, it takes to earn them back.
Should the illustrator get a royalty share or a flat fee?
It depends on how much the book will earn, which nobody knows at the start. Underneath, the choice is about who carries that risk: a share moves it onto the illustrator, a fee onto the author. Compare a 30% share with a flat $1,200.00 fee:
| Royalties over the period | Illustrator's 30% share | Flat fee |
|---|---|---|
| $2,000.00 | $600.00 | $1,200.00 |
| $4,000.00 | $1,200.00 | $1,200.00 |
| $8,000.00 | $2,400.00 | $1,200.00 |
The two are equal when the book earns $4,000.00 in royalties. Below that, the illustrator does better with the fee; above it, with the share. A share also lasts as long as the book sells, so the agreement needs to say for how long it runs. You can also combine the two: a smaller fee up front, repaid as a cost, plus a smaller share.
What about ads one of us pays for every month?
Treat ad spend like any other cost: whoever paid it is repaid from the next payment before the split. Say a month brings in $600 and Ben spent $150 on ads. Ben gets his $150 back, then the remaining $450.00 is split, so Ana receives $225.00 and Ben $375.00.
This only stays fair if both partners agree to the ad budget. Without a limit, one partner can spend the other's share. Put a monthly cap in writing, and agree what happens if ads cost more than the book earns that month. With the repay-first method the unpaid amount carries forward, exactly like the cover costs in Ana and Ben's ledger. To check whether ads are paying for themselves at all, see the guide on break-even ACoS.
What happens if one of us wants out?
The book doesn't stop selling when a partnership ends, and the royalties still arrive in one account. Decide in advance whether the departing partner keeps receiving their share for as long as the book sells, sells it to the other partner, or whether the book is unpublished. Also decide who can approve a new cover, a price change or a new edition once only one of you is involved. These are hard conversations to have after a falling-out and easy ones to have before the first upload.
A checklist for the written agreement
Keep it short and specific. It should answer:
- Whose KDP account publishes the book, and how the others see the sales reports.
- The split, written as a share of royalties received from KDP, for each format (ebook, paperback, hardcover).
- Which costs are repaid before the split, who paid them, and any limit on future costs such as a monthly ad budget.
- How soon after a KDP payment arrives the account holder passes on each share.
- Who decides on price, ads, categories, covers and new editions, and what needs both partners' agreement.
- For an illustrator: fee, share or both, and how long a share lasts.
- Who absorbs one-cent rounding differences when a payment doesn't divide evenly.
- What happens if a partner leaves, dies or wants the book unpublished.
Then keep the ledger going, one row per KDP payment in the same columns as Ana and Ben's, and send the latest version with every transfer. A partner who can check the arithmetic each month has no reason to ask about it later.