An alphabetical month axis can place April before February even when the original data is correctly dated. Physically rearranging the source rows is not the same as defining the order of a categorical label in the Power BI model.

Decide first whether the axis represents months within a year or successive months across several years. A Month Name label such as January does not distinguish January 2025 from January 2026. The intended grouping must be clear before you choose its ordering field.

Check the mapping before applying it

Power BI's Sort by Column requires the label and sort column to have matching granularity. Each distinct label must map to one sort value. For month-of-year labels, use a consistent whole-number mapping such as January=1, February=2 and March=3. Repeated January records should not acquire a different order number in another year.

Inspect a small sample containing two years. Include at least two rows for one month name and verify that their month numbers agree. A conflicting mapping is a data-definition problem; changing the chart's visual style will not resolve it.

In the current documented Power BI Desktop workflow, switch to Report view and select the label column in the Data pane. Open Column tools, Sort by Column and select the intended Month Number column. The configured column ordering applies to visuals using that label column.

Test the first, middle and final positions

Use January, February, March and December in the practice visual and confirm their month-of-year order. Check a second visual using the same label. Keep a known measure total alongside the exercise so an ordering correction does not conceal a changed selection or grouping.

For a continuous multi-year timeline, use a label that includes the year and an order key at that same level. As an original example, January 2025 and January 2026 can map to 202501 and 202601. A bare month number of 1 cannot establish which of those two labelled periods comes first.

Before handing over the report, read its labels and totals together. If several years intentionally combine into one January category, say so. If they must remain separate, confirm each year-month retains its own position and contribution. An accepted sort setting describes the intended analytical grain, not merely a visually familiar sequence of month names.

Sources: Microsoft: sort by column.