You don't tell us what the client's business is, but while this might be to do with tenants subsidising landlords, the term 'Aufloesung' suggests something else.

Essentially, subsidies of all kinds received in advance of the work/costs/purchases of assets/research programmes to which they relate are recognised as liabilities, since they represent deferred income. As the costs are incurred/assets are purchased etc etc the liability is then reversed to income in proportion to the cost or over the relevant period.

'Aufloesung von Baukostenzuschüssen' is therefore a fairly common income statement item for companies involved in constructing pretty much anything.

http://www.google.co.uk/search?hl=en&q=Auflösung von Baukost...

'Income from the reversal of deferred income from network subsidies'
http://www1.financialreports.evn.at/2005-06/gb/en/notes/note...