# Customize patching in Accelerate
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Patching ensures that your software is up-to-date and meets your compliance policies.

**When to patch**: Patching occurs during a *maintenance window*. You can schedule maintenance windows so that patches are only applied during preset times.

**What to patch**: You have to associate the Amazon EC2 instances you want to patch with a maintenance window. To associate the instances with a maintenance window, the Amazon EC2 instances must be tagged, and the maintenance window should have those tags as a target.

**Which patches to install**: Using patch baselines, you set rules to auto-approve certain types of patches, such as operating system or high-severity patches. You can also specify exceptions to your rules, for example, lists of patches that are always approved or rejected.
+ For general patching recommendations, see [Patching recommendations](acc-patching.md#acc-patching-recos).
+ To create custom maintenance windows, see [Create a patch maintenance window in AMS](acc-p-maint-window.md).
+ To create custom patch baselines, see [Custom patch baseline with AMS Accelerate](acc-patch-baseline-custom.md).
+ To route patch alerts to the resource owner, see [Understand patch notifications and patch failures in AMS Accelerate](acc-patch-mon-remediate.md).