CRM deleted deals are automatically removed from your QuarterOne data weekly. In the case that you may need to remove them sooner, you can do so by doing a Full Sync.
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You can trigger a full sync by clicking on the "sync all records here" link in Settings > Data&CRM. A full sync takes longer than the "Sync now" in the Pipeline and Dashboard pages, but it makes sure that there are no missing or extra data compared to your CRM account.

A full sync can also be used if there are missing Client or Account information in QuarterOne.