Updating a fixed cost.

Updating a fixed cost uses the same pattern as retiring one: end the existing version, start a new version. This protects every past P&L from silently recomputing when reality changes — your March numbers always show March's rent, even after October's rent bump.

01 Why can't I just edit the amount in place?

Because changing the amount on an existing fixed cost would make every past day's P&L silently recompute against the new number. Your March P&L (when rent was €2.800) would suddenly show €3.000 of rent just because you signed a new lease in October — a lie about the past that breaks any reconciliation with your bookkeeper. Instead, end the old version and start a new one, so March always shows March's rent. The two-step pattern below is how.

02 What is the two-step update pattern?

1. 1
   End the old cost

   Open the existing fixed cost. Set its end date to the day before the change.

2. 2
   Add a new cost

   Click + Add fixed cost. Name it the same thing, type the new amount, set the start date to the day of the change.

3. 3
   Save

   Past days subtract the old amount. New days subtract the new one. Past P&Ls stay honest.

03 When is editing in place actually fine?

In-place editing is fine for cosmetic changes — fixing a typo in the name or adding a note — because those don't affect any past P&L. It's the amount and frequency that trigger the recommend-replace pattern, since those are what change your historical numbers. nouz nudges you toward end-old-start-new when it spots an amount or frequency edit on a fixed cost that's been active for more than seven days.

04 What are common scenarios for updating a fixed cost?

Three real-world cases all use the end-old-start-new pattern. A rent increase at lease renewal: end the old line on Dec 31, start the new one on Jan 1. Switching providers: end the old internet line, start the new fibre line. Adding a part-timer: either replace the "Staff" line with a higher one or add a separate "Saturday helper" line — the second is more readable for future you. The list below works through each.

• Rent increase. Lease renewal raises rent from €2.800 to €3.000 on January 1st. End the old line on Dec 31, start the new line on Jan 1.
• Switching providers. Old internet at €95/month, new fibre at €120/month from October 1st. End the old line, start the new line — could keep the same "Internet" name or distinguish "Internet (DSL)" vs "Internet (fibre)".
• Adding a part-timer. Base staff cost was €7.200/month, now you're adding €1.200 for a Saturday helper starting March. Two options: end the old "Staff" line and start a new "Staff" line at €8.400, or add a separate "Saturday helper" line at €1.200. The second is more readable for future you.