Fix issue with Split reverting was not successful for expense with negative amount

[ZhenjaHorbach]

Explanation of Change

Fixed Issues

$ #82575
PROPOSAL:

Tests

1. Open App
2. Create a workspace expense with negative amount
3. Press More button and choose Split
4. On the splits screen, press save to create a few splits
5. After creating splits, open any split and in More menu, press Edit split
6. On the splits screen- remove split
7. Press Save
8. Verify that the split reverting must be successful for expense with negative amount.

• Verify that no errors appear in the JS console

Offline tests

QA Steps

// TODO: These must be filled out, or the issue title must include "[No QA]."

• Verify that no errors appear in the JS console

PR Author Checklist

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Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

2026-03-10.10.50.28.mov

[melvin-bot]

@ShridharGoel Please copy/paste the Reviewer Checklist from here into a new comment on this PR and complete it. If you have the K2 extension, you can simply click: [this button]

[codecov]

Codecov Report

✅ Changes either increased or maintained existing code coverage, great job!

Files with missing lines	Coverage Δ
src/libs/SplitExpenseUtils.ts	100.00% <100.00%> (ø)
src/pages/iou/SplitExpensePage.tsx	0.00% <0.00%> (ø)
... and 451 files with indirect coverage changes

[trjExpensify]

PR for a WN project. 👍

[ShridharGoel]

Reviewer Checklist

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  • I verified any copy / text shown in the product is localized by adding it to src/languages/* files and using the translation method
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Screenshots/Videos

Android: HybridApp

Android: mWeb Chrome

iOS: HybridApp

Screen.Recording.2026-04-10.at.6.21.24.PM.mov

iOS: mWeb Safari

Screen.Recording.2026-04-10.at.6.40.42.PM.mov

MacOS: Chrome / Safari

Screen.Recording.2026-04-10.at.6.38.23.PM.mov

[ShridharGoel]

Bug: Mixed-sign negative splits are still validated with signed comparisons in SplitExpensePage. So, it does not allow saving the expense even when the final amount is lower.

Screen.Recording.2026-03-12.at.12.21.35.AM.mov

[ZhenjaHorbach]

Bug: Mixed-sign negative splits are still validated with signed comparisons in SplitExpensePage. So, it does not allow saving the expense even when the final amount is lower.

Screen.Recording.2026-03-12.at.12.21.35.AM.mov

When original amount is negative and the last split is positive
I think it's okay show the error

But in case the last split is negative and bigger than the original(which is also negative)
Then agree
We don't need to show the error in this case

[ZhenjaHorbach]

Actually, we have a BE issue
When I have a few negative amounts (-1,-1,-4), which in sum are bigger than the original amount (-10)
But since we decided to use math abs
It should be valid case ( (abs(-6) => 6) < (abs(-10) => 10))
So we can save these splits and there shouldn't be any BE error here

CC:@lakchote

2026-03-11.20.53.34.mov

[ZhenjaHorbach]

Still waiting BE fixes

[lakchote]

this should be fixed now @ZhenjaHorbach

[ZhenjaHorbach]

@ShridharGoel
I suppose you can continue the review

[ShridharGoel]

Bug: Shows -43 as being greater than -22 (probably comparing absolute values)

Screen.Recording.2026-03-29.at.6.57.31.PM.mov

[ZhenjaHorbach]

Bug: Shows -43 as being greater than -22 (probably comparing absolute values)

Screen.Recording.2026-03-29.at.6.57.31.PM.mov

Oh
Actually yes
But I don't know how we should handle this

@lakchote @garrettmknight @trjExpensify
Could you check this issue?
And which error text do we need to use?

On one side, we need to show less than the original value error (-43 < -22)
But on the other side, since technically we use absolute values, it's okay to show greater than the original value error (43 > 22)

[ZhenjaHorbach]

Bug: Shows -43 as being greater than -22 (probably comparing absolute values)
Screen.Recording.2026-03-29.at.6.57.31.PM.mov

Oh Actually yes But I don't know how we should handle this

@lakchote @garrettmknight @trjExpensify Could you check this issue? And which error text do we need to use?

On one side, we need to show less than the original value error (-43 < -22) But on the other side, since technically we use absolute values, it's okay to show greater than the original value error (43 > 22)

@lakchote @garrettmknight @trjExpensify
Friendly bump!

[lakchote]

@ZhenjaHorbach

Based on the earlier decision in this comment and the backend fix that followed, same-sign negative totals are validated by magnitude, so -43 vs -22 is treated as 43 > 22, not as a -43 < -22 “less than” case.

The current behavior seems correct, but the copy is confusing for negative totals. If we want clearer wording, I’d suggest something specific for them, like "Total split amount exceeds the original expense amount". Thoughts @garrettmknight?

[ZhenjaHorbach]

@ZhenjaHorbach

Based on the earlier decision in this comment and the backend fix that followed, same-sign negative totals are validated by magnitude, so -43 vs -22 is treated as 43 > 22, not as a -43 < -22 “less than” case.

The current behavior seems correct, but the copy is confusing for negative totals. If we want clearer wording, I’d suggest something specific for them, like "Total split amount exceeds the original expense amount". Thoughts @garrettmknight?

Yes
Everything is fine with the behavior
But what text we should use is a bit unclear 😅

[garrettmknight]

The current behavior seems correct, but the copy is confusing for negative totals. If we want clearer wording, I’d suggest something specific for them, like "Total split amount exceeds the original expense amount". Thoughts @garrettmknight?

I'm not convinced we need to update the copy:

• We show the original amount. Ex. -$10
• We show the existing split amount. Ex. -$5
• We show the difference they need to correct in the error Total amount is £5.00 greater than the original expense.

I'm not sure making it more general will actually help in this case, and I'm not sure how we could be more specific.

[ZhenjaHorbach]

The current behavior seems correct, but the copy is confusing for negative totals. If we want clearer wording, I’d suggest something specific for them, like "Total split amount exceeds the original expense amount". Thoughts @garrettmknight?

I'm not convinced we need to update the copy:

• We show the original amount. Ex. -$10
• We show the existing split amount. Ex. -$5
• We show the difference they need to correct in the error Total amount is £5.00 greater than the original expense.

I'm not sure making it more general will actually help in this case, and I'm not sure how we could be more specific.

At the moment, we show Total amount is £5.00 less than the original expense in this case
Since we use absolute values under the hood

[garrettmknight]

Looks like it's Total amount is £5.00 greater than the original expense. on staging and prod, which makes logical sense to me in this situation. Let's take a quick step back, though:

@MelvinBot can you confirm the behavior for reverting a split in general is:

1. Open App
2. Create a workspace expense
3. Press More button and choose Split
4. On the splits screen, press save to create a few splits
5. After creating splits, open any split and in More menu, press Edit split
6. On the splits screen remove all splits except one
7. Press Save
8. Verify that the split is reverted: It returns to it's original amount and can be resplit again.

[MelvinBot]

Yes, that flow is correct. When you edit a split and remove all splits except one, the app detects this as a "reverse split operation" and calls REVERT_SPLIT_TRANSACTION instead of the normal split update API.

The detection logic is in Split.ts:1071-1072 — it triggers when splitExpenses.length === 1 and there were originally multiple child transactions. On revert, the expense returns to its original unsplit state and can be re-split again.

So the expected behavior for those steps is:

1. Create workspace expense
2. Split it
3. Edit split → remove all but one
4. Save → split is reverted, expense returns to original amount, and it's splittable again

This is the same behavior on staging, prod, and in this PR's branch.

[garrettmknight]

Melv is wrong - we don't revert to the original expense amount, nor is that the intention. So I think the behavior is right from my testing on prod and staging. The thing we need to change is any test that indicates the amount should be changed. Does that make sense @ZhenjaHorbach ? Can you test and confirm you're seeing the same as me in this comment?

[ZhenjaHorbach]

Melv is wrong - we don't revert to the original expense amount, nor is that the intention. So I think the behavior is right from my testing on prod and staging. The thing we need to change is any test that indicates the amount should be changed. Does that make sense @ZhenjaHorbach ? Can you test and confirm you're seeing the same as me in this comment?

I'm confused 😅
As far as I remember, we agreed that this is a valid case, and we can revert this split

We show the original amount. Ex. -$10
We show the existing split amount. Ex. -$5
But since we decided to use absolute values ​​in case the original transaction and splits have the same signs
These values ​​become:
-$10 => $10 > -$5 => $5

As a result, we just show the warning, but we are able to revert, and the reverted transaction will have -$5 amount

CC: @lakchote

[garrettmknight]

Oh, now I get what you're saying about the abs values.

As a result, we just show the warning, but we are able to revert, and the reverted transaction will have -$5 amount

This makes sense then. The copy stays the same, but you're able to save the edit/revert the expense.

[ZhenjaHorbach]

Oh, now I get what you're saying about the abs values.

As a result, we just show the warning, but we are able to revert, and the reverted transaction will have -$5 amount

This makes sense then. The copy stays the same, but you're able to save the edit/revert the expense.

---

We show the original amount. Ex. -$10
We show the existing split amount. Ex. -$5

So in this case, we will show Total amount is $5.00 greater than the original expense warning
Right?

[garrettmknight]

So in this case, we will show Total amount is $5.00 greater than the original expense warning
Right?

Yeah, I think that's right.

[ZhenjaHorbach]

Okay then
It's good that we finally figured this out 😅
Thanks!

[ZhenjaHorbach]

In this case, I need to make a few improvements
I will complete on Monday

[ZhenjaHorbach]

Okay
I think I fixed all the issues

But found a new one when we added a new split
The new split has an incorrect amount
But I think we can fix it in a separate PR since it's not related to the current issue

2026-04-07.16.39.16.mov

[ZhenjaHorbach]

@ShridharGoel
It's ready for retesting!

[ShridharGoel]

Noticed that after the revert, the expense shows as a duplicate. Maybe we need to check this from the backend side?

[melvin-bot]

We did not find an internal engineer to review this PR, trying to assign a random engineer to #82575 as well as to this PR... Please reach out for help on Slack if no one gets assigned!

[ZhenjaHorbach]

Noticed that after the revert, the expense shows as a duplicate. Maybe we need to check this from the backend side?

Probably yes
But it's not our
Since we just updated error and warning validations

[stitesExpensify]

@ZhenjaHorbach can you please add qa steps?

[stitesExpensify]

LGTM but there is one issue in the errors and there are no QA steps

[stitesExpensify]

This is incorrect right? We are returning "LESS"?

[stitesExpensify]

@ZhenjaHorbach can you clarify why you decided to remove the test instead of just changing it to greater?

[ZhenjaHorbach]

@ZhenjaHorbach can you clarify why you decided to remove the test instead of just changing it to greater?

Because we already have 2 tests for less and greater for the mixed-sign splits cases
So the removed test seems redundant
https://github.com/Expensify/App/pull/84705/changes#diff-5490822fa83d6f50fa4f9063eb17bf1f74c247ace1e508634a9a3c2a3a788a1dR112-R132

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