[Duplicate Expenses] Add Per Diem Expense Support

[jjcoffee]

Explanation of Change

Fixed Issues

$ #76829
PROPOSAL:

Tests

Same as QA.

• Verify that no errors appear in the JS console

Offline tests

Same as QA.

QA Steps

Pre-requisite

• Have a per diem expense created before 2025-12-30 (when the BE PR was deployed)

1. Open the existing per diem expense, open the More menu and verify that there is no Duplicate option
2. Create a per diem expense
3. Log out and back in
4. Open the expense
5. Go to More -> Duplicate
6. Verify that the expense gets duplicated
7. Open the duplicated expense and verify that all the information is the same as the original expense, except for the date, which is set to today's date.

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android: Native
  • Android: mWeb Chrome
  • iOS: Native
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I verified there are no new alerts related to the canBeMissing param for useOnyx
• I followed proper code patterns (see Reviewing the code)
  • I verified that any callback methods that were added or modified are named for what the method does and never what callback they handle (i.e. toggleReport and not onIconClick)
  • I verified that comments were added to code that is not self explanatory
  • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
  • I verified any copy / text shown in the product is localized by adding it to src/languages/* files and using the translation method
    • If any non-english text was added/modified, I used JaimeGPT to get English > Spanish translation. I then posted it in #expensify-open-source and it was approved by an internal Expensify engineer. Link to Slack message:
  • I verified all numbers, amounts, dates and phone numbers shown in the product are using the localization methods
  • I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is either coming verbatim from figma or has been approved by marketing (in order to get marketing approval, ask the Bug Zero team member to add the Waiting for copy label to the issue)
  • I verified proper file naming conventions were followed for any new files or renamed files. All non-platform specific files are named after what they export and are not named "index.js". All platform-specific files are named for the platform the code supports as outlined in the README.
  • I verified the JSDocs style guidelines (in STYLE.md) were followed
• If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
• I followed the guidelines as stated in the Review Guidelines
• I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
• I verified all code is DRY (the PR doesn't include any logic written more than once, with the exception of tests)
• I verified any variables that can be defined as constants (ie. in CONST.ts or at the top of the file that uses the constant) are defined as such
• I verified that if a function's arguments changed that all usages have also been updated correctly
• If any new file was added I verified that:
  • The file has a description of what it does and/or why is needed at the top of the file if the code is not self explanatory
• If a new CSS style is added I verified that:
  • A similar style doesn't already exist
  • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG))
• If new assets were added or existing ones were modified, I verified that:
  • The assets are optimized and compressed (for SVG files, run npm run compress-svg)
  • The assets load correctly across all supported platforms.
• If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
  • I verified that all the inputs inside a form are aligned with each other.
  • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
• If a new page is added, I verified it's using the ScrollView component to make it scrollable when more elements are added to the page.
• I added unit tests for any new feature or bug fix in this PR to help automatically prevent regressions in this user flow.
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.

Screenshots/Videos

Android: Native

android-app-2026-01-07_12.19.05.mp4

Android: mWeb Chrome

android-chrome-2026-01-07_12.22.13.mp4

iOS: Native

ios-app-2026-01-07_12.06.31.mp4

iOS: mWeb Safari

ios-safari-2026-01-07_12.08.51.mp4

MacOS: Chrome / Safari

Old expense

desktop-chrome-2026-01-07_11.28.14.mp4

Normal flow

desktop-chrome-2026-01-07_11.59.58.mp4

[codecov]

Codecov Report

❌ Looks like you've decreased code coverage for some files. Please write tests to increase, or at least maintain, the existing level of code coverage. See our documentation here for how to interpret this table.

Files with missing lines	Coverage Δ
src/libs/ReportSecondaryActionUtils.ts	91.62% <75.00%> (-0.18%)	⬇️
src/libs/actions/IOU/index.ts	67.55% <33.33%> (+0.15%)	⬆️
... and 35 files with indirect coverage changes

[jjcoffee]

@JS00001 This is testing quite well now, but I'm getting an "unexpected error occurred" when duplicating from a non-default workspace. As far as I can tell all the necessary params are being passed, so it's a bit difficult to debug with a generic error like that 😄 Are you able to help track down what the actual error is on the BE? Request ID: 9ba2e848bcee8825-SJC.

[melvin-bot]

@hoangzinh 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]

[JS00001]

Lookin good, will wait on @hoangzinh 's review

[jjcoffee]

@JS00001 Did you catch my comment here?

[JS00001]

I missed that, let me look, sorry about that

[JS00001]

Looks like this is a BE issue with padding a custom unit that doesnt match the policy we are creating the expense in

[JS00001]

@jjcoffee Why do we not duplicate the distance expense to the same workspace? Why move it to the default?

[jjcoffee]

@jjcoffee Why do we not duplicate the distance expense to the same workspace? Why move it to the default?

@JS00001 I don't know the underlying product reason, but that's the expected behaviour from the original issue (not specific to distance expenses), and is what happens on OD.

From #65948:

We create an expense on the user's primary workspace with the following details, using the CreateMoneyRequest command

[jjcoffee]

Looks like this is a BE issue with padding a custom unit that doesnt match the policy we are creating the expense in

@JS00001 Are there any semi-recent changes there? I could swear it worked before on the original PR, because I remember testing to make sure an invalid rate error would come up (the same way it does if moving a per diem to a different workspace) following the same process of duplicating from a non-default workspace.

[JS00001]

It looks like we've been throwing that for 13 months, I'm looking at changing this

[JS00001]

@jjcoffee Lets go with the same solution as Distance rates got. I'm going to update CreatePerDiemRequest to accept a customUnitPolicyID parameter. I'll need to make some BE changes, but could you work on the FE changes for this?

[JS00001]

Tested the PR with a hard-coded customUnitPolicyID, and it works as expected, will get those BE prs reviewed now

[trjExpensify]

WN project, all good from me with adding support for this! 👍