français vers anglais Affaires / Finance Finance (général) invoicing system

The context is a French (France, I mean, as against Belgian or Swiss or Canadian) requirements spec for an invoice monitoring and approval system for an IT Dept (the actual payment is looked after elsewhere via an interface). "Atterrissage" occurs twice:

1.Il (the current system) fournit, une situation des engagements et des dépenses par rapport au budget afin de connaître le solde disponible pour l’année en cours ainsi que l’atterrissage probable en fin d’année.
Then, when discussing the SLA for the new system, which does everything the old system does plus more:
2. Continuité de service : qualité de service requise lors des atterrissages budgétaires du fait des contraintes de clôtures comptables.

Note, if it helps, w.r.t. 1. that the IT Dept is considered to generate only costs, no income, hence the reference to the available balance once budget commitments and known expenditure are taken into account.
"Atterrissage" is clearly something that happens at year-end. I can find the word only in its "landing"/"landfall" sense in my dictionaries and on-line glossaries.
Not having spotted the second reference to "atterrissage" when I started the translation, I translated it the first time with the vague "end result", thinking in terms of over-budget/under-budget surplus/deficit kinda thing. I'm aware, of course, that "variance" can be used for this. So I'm wondering whether, since this refers to the activity and not the variance itself, a term such as "variance calculation" would be appropriate. Have any of you come across "atterrissage" used in such a way before? Any other suggestions? I'm thinking it can't just be "closing the accounts" since this is one of the constraints on the "atterrissage" process....