How to model revenue or cost growth over time in sherloc

If a line changes by a similar amount every month (revenue climbing steadily, a cost creeping up), you can model that growth once, rather than editing every month by hand.

1. Decide how the line should grow

Work out whether it grows by a fixed amount each month, or by a percentage each month.

Example: revenue of £50,000 growing 3% a month, or a cost line increasing by a flat £200 a month.

2. Add it as an assumption

Select Create assumption. In the Create Assumption drawer, give the assumption a name (this is required), choose the sheet from the Select the sheet impacted by the assumption dropdown, then tick the line you want to grow. Select Continue to date range.

Choose All months for growth that carries on through the whole forecast, or Date range for a set run of months. Then select Continue to criteria.

Choose Consecutive monthly change (“A cumulative change that increases or decreases every month”). Under Change by, pick £ Fixed amount or % Percentage, enter it in Change each month, and select Add assumption.

Consecutive monthly change needs a period of at least two months in a row, so it isn't available for a single month or for months that aren't next to each other.

3. Check the numbers

Look at the line across several months to confirm it's growing the way you expect. The change starts in the first month you selected, and each month builds on the one before: a percentage compounds, while a fixed amount adds the same figure each time.

Example: £50,000 growing 3% a month from January. January is already £51,500, then February is £53,045, and so on. A fixed £200 gives a line that is £200 higher in the first month, £400 higher in the second, and so on.

When the period ends, the line returns to its base figure. If you want the growth to carry on, choose All months.