By default, all the transactions in a category are smoothed out and projected forward. Depending on how much history you have, one unusually expensive month will not throw off the projection, but may still have some impact. On top of that, there are a few tools available to improve the forecast:

1. Exclusions. You can exclude any single transaction from the forecast. It stays in your history but no longer counts toward the projection.

2. Streams. You can group a set of transactions into a stream (e.g. your YouTube subscription inside Entertainment), and it gets its own projection on its own schedule instead of being averaged into the category.

3. Plans. If you know a big expense is coming, you can set up a Plan. Plans can add one-off events (like an expensive car repair) or apply a percentage increase/decrease to a category (like Shopping during the holidays).

Finally, once there’s enough history, the forecast also picks up seasonal patterns, like higher spending in Shopping or Travel in December, and will project higher amounts for just that month. Your first December may be underestimated, but it gets more accurate as history builds up.