How to safely delete .inProgress Time Machine backup? I attempted to start a Time Machine backup but the backup failed due to insufficient space. I now have a useless 60 GB .inProgress file that's eating into my already limited storage space.
For a seemingly easily-achieved problem, there are few resources online for this. A pre-Catalina article from 2018 suggests using tmutil delete /path, as do these Ask Different answers. All of these answers are also pre-Catalina.*
With such consensus of answers I tried sudo tmutil /path/backup.inProgress but received a return message of &quot;Invalid deletion target (error 22)&quot; and &quot;Total Deleted: 0B&quot;
$ sudo tmutil delete /Volumes/XXXX/Backups.backupdb/XXXX/2020-09-30-004400.inProgress
Password:
/Volumes/XXXX/Backups.backupdb/XXXX/2020-09-30-004400.inProgress: Invalid deletion target (error 22)
Total deleted: 0B

Also, when I run tmutil listbackups Terminal only prints completed backups (as the manual indicates should be the case).
How can I safely delete the 60 GB .inProgress file?
*This answer suggests simply dragging the .inProgress file into the Trash – though from personal experience I know this is wrong and leads to problems – namely a perpetually stuck Time Machine and an impossible to empty Trash.
The next backup interval prunes and cleans this folder. If you have 24 hours of backups and still have a hung inProgress, I would open a case directly with Apple.
With hard links, it’s unlikely you are using any space on these files, since another interval already covers them or the next interval will reuse that space.

The risk of messing with the backups is you ruin that destination so unless you are willing to make that destination read-only and start backing up to a new destination, I would not mess with this manually - even to try to convince tmutil to delete that non-interval.
I have had great success using time machine utility to delete whole backups and letting the system run to pre-clean and post-clean these progress folders. When the progress folder remains for more than a day of successful backups, you usually have another problem and poking at a system with one failure isn’t likely to address the main problem. You could also try to bypass and clean up a large file if that helps you get space back if deleting intervals doesn’t prune enough space.