7 Property operating expenses
| | 2018 | 2017 |
Taxes | 7,405 | 7,869 |
Insurance | 467 | 222 |
Maintenance | 25,724 | 25,727 |
Valuation fees | 598 | 476 |
Property management fees | 3,901 | 3,438 |
Promotion and marketing | 714 | 432 |
Letting and lease renewal fees | 5,284 | 5,877 |
Other operating expenses | 9,173 | 11,374 |
Addition to provision for bad debts | 273 | 425 |
Total property operating expenses | 53,539 | 55,840 |
In 2018, € 0.6 million (2017: € 0.5 million) of the maintenance expenses related to unlet properties.