How to model a seasonal or one-off cost in sherloc

1. Confirm the cost and the months it applies to

Work out how much extra cost you want in each month, and exactly which months it falls in: this might be one month, or a short run of months.

Example: taking on extra temporary staff over the festive period, at an extra £2,000 in each of November and December.

2. Add it as an assumption on the relevant line

Select Create assumption. In the Create Assumption drawer, give the assumption a name (this is required), then choose the sheet that holds your costs from the Select the sheet impacted by the assumption dropdown: for example Profit And Loss. Tick the cost line it applies to in the list of row items, then select Continue to date range.

Under When should the assumption happen, choose Date range and set a From and To month, covering just the months the cost applies to, not the whole year. If the months aren't next to each other, choose Specific months instead. Then select Continue to criteria.

Under What the assumption is modelling, choose Increase / decrease, keep £ Fixed amount selected, and enter the extra cost for one month in How much? (or choose Replace the figure if you'd rather set the month to a figure than add to it). Finish with Add assumption.

The amount you enter is applied to each month you've selected, so it isn't shared out between them.

Example: enter 2,000 for November and December. £2,000 is added to each of the two months, so £4,000 in total.

3. Check the numbers

Look at your Profit And Loss sheet to confirm the cost only appears in the months you selected, and that your other months are unaffected. Under Accounts & Assumption Details you can see the line's Base figure, your assumption and the Result for each month.