## TL;DR

Rydoo computes per diem from the trip's start and end timestamps against your company's rate table. Confirm the travel dates and times are entered (including time zones), check the destination's rate is configured, and recalculate; missing times are the most common cause.

## Error

```text
Rydoo: per diem calculation failed
```

## Steps

1. Open the trip in Rydoo and check that departure and return dates AND times are filled in. Expected: both timestamps are present.
2. Verify the time zone on the trip matches where travel occurred. Expected: no off-by-hours shift from a wrong zone.
3. Check that a per diem rate exists for the destination country or city in your Rydoo policy. Expected: the rate table covers the destination.
4. Correct the missing data and trigger a recalculation. Expected: Rydoo computes the per diem amount.
5. Sanity-check the result against the expected days times the daily rate. Expected: the math matches your estimate.

## When to use

- Rydoo fails to calculate a per diem or shows zero unexpectedly.
- The trip spans time zones or multiple destinations.

## When not to use

- The per diem calculates but the partial-day amount looks wrong (see the partial-day skill).
- The rate itself is wrong (ask your admin to update the rate table).

## Tool compatibility

- Rydoo travel and expense; per diem rates configured by the Rydoo admin.

## Variant phrasings

### Per diem could not be calculated

Same failure, alternate wording.

### Missing rate for per diem calculation

The destination has no configured rate.

## Why it happens

Per diem math needs complete inputs: timestamps, time zone, and a rate for the destination. Any missing piece aborts the calculation instead of producing a wrong number.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_B3vIDzsVJ0X91cam7EbErg