## TL;DR
Time Machine network backups live in a sparsebundle disk image on the NAS, and verification failing means that image filesystem or its bands are damaged. Attach and check the sparsebundle with disk utilities while Time Machine is paused, review NAS health and free space, repair if the damage is minor, and if verification still fails, archive the old bundle aside and start a fresh backup rather than trusting it.

```text
time machine sparsebundle verification failed
```

## Use this when
- Time Machine reports verification failed for a network backup and offers to start a new backup.
- The Mac can browse some backups but the newest state is flagged bad.
- The NAS hosting the bundle had a power or firmware event.

## Not for this skill when
- A local directly attached Time Machine disk fails checks. Similar tools, different target handling.
- Time Machine cannot find the target at all. Discovery and network first.

## Steps
1. Pause Time Machine and note the sparsebundle name and size on the NAS share. Verify: the bundle is identified and backups are paused
2. Check NAS health, free space and recent events for the volume holding the bundle. Verify: NAS-side faults are found or cleared
3. Mount the sparsebundle on the Mac and run a filesystem check on its volume, capturing errors. Verify: check results are recorded
4. If repairs succeed, run Time Machine verification again from its menu. Verify: verification passes or still fails with the same errors
5. If it still fails, rename the old bundle to keep it for possible manual file recovery and start a new backup. Verify: a fresh backup completes and verifies

## Variant phrasings
### time machine sparsebundle corrupted nas verify
The NAS phrasing.
### time machine verification failed start new backup
The prompt variant.
### sparsebundle fsck failed time machine
The filesystem wording.

Compatibility: macOS 13 to 15 Time Machine to SMB shares on Synology, QNAP, TrueNAS and macOS servers, sparsebundle format network backups.

## Why it happens
A network Time Machine backup is a filesystem inside a disk image inside a network share, three layers that can each corrupt the others when writes are interrupted. Sparsebundle bands spread across the share mean a NAS event can damage parts invisibly until verification reads them. Local USB backups skip the image layer, which is why their failures look different.

## Edge cases / pitfalls
- Never run filesystem repair on the bundle while Time Machine might mount it. Pause and eject everywhere first.
- Copying a sparsebundle for safekeeping must include all bands. Partial copies are useless.
- Frequent bundle damage on one NAS usually means the share drops connections under load. Fix the NAS or network, not just the bundle.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_fkVN0BGVnnOlHOL-vCY8HQ