7 Property operating expenses
| | 2017 | 2016 |
Taxes | 7,869 | 7,669 |
Insurance | 222 | 162 |
Maintenance | 25,727 | 23,276 |
Valuation fees | 476 | 748 |
Property management fees | 3,438 | 3,136 |
Promotion and marketing | 432 | 436 |
Letting and lease renewal fees | 5,877 | 4,958 |
Other operating expenses | 11,374 | 6,852 |
Addition to provision for bad debts | 425 | 493 |
Total property operating expenses | 55,840 | 47,730 |
In 2017, € 0.6 million (2016: € 0.5 million) of the maintenance expenses related to unlet properties.