> For the complete documentation index, see [llms.txt](https://help.tahua.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.tahua.io/knowledge-base/integrations-help-guides/xero/xero-faqs/syncing-milestone-errors.md). # Syncing Milestone Errors If a Tahua Milestone cannot be synced with Xero, an email advising that the sync was unsuccessful will be sent. This can happen for a number of reasons - usually because the bill in Xero is in a state that doesn't allow it to be updated (i.e. it has already been approved, voided, or paid), or it falls within a [locked period](/knowledge-base/integrations-help-guides/xero/xero-faqs/syncing-milestone-errors/lock-dates-and-xero-syncing.md). You will need to resolve this in Xero before resyncing the Milestone by using the link supplied in the email you received. Alongside the "resync link", the syncing error email will provide links (if available) through to the Milestone, Application, Contract and Xero Bill, which will enable you/your accountant to figure out what has happened and why. **Exempting a milestone from syncing** If a milestone should never be pushed to Xero (for example, it doesn't require an invoice and doesn't need to trigger a payment), you can mark it as exempt from Xero syncing on the Milestone page. This will prevent future sync attempts and error emails for that milestone. You don't need to exempt [Organisation-supplied Milestones](/knowledge-base/administrator-help-guides/milestones/organisation-supplied-milestones.md) (shown with a **Supplied by us** label). Their Payments are **incoming**, money owed to your organisation, so Tahua never syncs them to Xero and they won't produce sync error emails.