6 Gross rental income and service charge income
| | 2018 | 2017 |
Theoretical rent | 213,376 | 197,895 |
Incentives | (928) | (1,073) |
Vacancies | (5,354) | (4,358) |
Total gross rental income | 207,094 | 192,464 |
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 € 5.5 million (2017: € 4.9 million) receivable from tenants for the services utilities, caretakers, etc. when the Fund acts as a principal.