Yes, you need a trekking permit for Poon Hill. One requires collecting/ obtaining two types of trekking permits: TIMS Card and Annapurna Conservation Area Entry Permit. The TIMS Card costs Rs. 2000 and the Annapurna Conservation Area Entry Permit costs Rs. 3000. You can easily obtain these Poon Hill Trekking permits from the Nepal Tourism Board office located in Kathmandu or most of the trekkers obtain these permits via their trekking partners/trekking agents located in Nepal/Kathmandu. For this, you can provide your passport copy and passport sized photographs. If you go up to only Australian Camp via Dhampus, you don’t require any kind of trekking permits, but if you pass Pothana and then to Landruk and Ghandruk or Ulleri through Nayapool and Birethanti, you at any cost need to have ACAP but TIMS card is not necessarily to have these days.