More than 140,000 letters to Santa have been sent this year, with most Irish boys and girls on the 'nice list', according to An Post.
Letters to the big man started arriving in post offices as early as July, but letters are only delivered to the North Pole closer to Christmas.
A lot of letters are also full of surprises for the elves, including glitter, soothers and half-eaten sweets.
Getting all the letters ready for Santa takes a lot of time, according to An Post's Communications Executive Eimear Breen.
"Once a child posts a letter, it goes through our system within four hours and then it's all put aside for the elves," she said.
"For the turnaround then, Santa sends all the post back by the last day of posting. They'll be in the system by the 19th."
Most children are sensible when it comes to the quantity of presents they want, but some are hoping for dozens of presents from Santa.
"We've come across letters with an awful lot of presents on the wish list. One of the elves told me there was around 44 items on the list. They were a bit surprised about this. Normally it's two or three items plus a surprise."
"A lot of the children this year seem to be asking for lego. It seems to be one of the favourite toys this years. Vouchers, money, moshi monsters and furbies and all sorts like that seem to be popular across the board."
For those who don't have their lists sent off, it may be a bit too late for a reply, but Santa will still get it in time.
"Santa always tries to reply to all of them, but last dates for posting is obviously very important for the North Pole and for us in An Post," she said.
"it's fantastic. It's usually the first letter for a child to write, so it's very important from that aspect. When they're writing to Santa they put an awful lot of thought into it and this thought process can go on for months before they actually put pen to paper.
"There are some sad letters. One of the elves mentioned a letter that they wanted to replace their mam's jewellery box because it had been stolen from the house. You'll always get the sad story in, if there's been a bereavement in the family. It can be hard reading those."