6 Gross rental income and service charge income
| | 2016 | 2015 |
Theoretical rent | 180,677 | 167,986 |
Incentives | (1,042) | (1,378) |
Vacancies | (4,128) | (3,994) |
Total gross rental income | 175,507 | 162,614 |
The Fund leases its property investments in the form of non-cancellable operating leases. The nature of the theoretical rent has an indefinite duration because there are no fixed contract periods.
Service charge income represents € 4.4 million (2015: € 4.1 million) income receivable from tenants for the services of utilities, caretakers, etc. when the Fund acts as principal.