6 Gross rental income and service charge income
| | 2017 | 2016 |
Theoretical rent | 197,895 | 180,677 |
Incentives | (1,073) | (1,042) |
Vacancies | (4,358) | (4,128) |
Total gross rental income | 192,464 | 175,507 |
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 amounted to € 4.9 million (2016: € 4.4 million) receivable from tenants for the services utilities, caretakers, etc. when the Fund acts as a principal.