7 Property operating expenses
| | 2017 | 2016 |
Taxes | 1,872 | 1,315 |
Insurance | 163 | 164 |
Maintenance | 1,428 | 1,738 |
Valuation fees | 159 | 85 |
Property management fees | 898 | 811 |
Promotion and marketing | 273 | 195 |
Letting and lease renewal fees | 686 | 498 |
Other operating expenses | 1,375 | 1,221 |
Addition to provision for bad debts | 40 | 544 |
Total property operating expenses | 6,894 | 6,571 |
In 2017, € 0.1 million (2016: € 0.2 million) of the maintenance expenses related to unlet properties.