Australians could have thousands more dollars in their wallet than they think with rare coins or any with small errors coveted by collectors.
Some rare error coins, which slip past inspectors during the minting process, are sought after by collectors who can try to outbid each other - driving the price up.
A TikTok user pointed out some sought-after rare or 'mistake' coins in a video uploaded on Sunday - including a 'Remembrance Day' red poppy $2 coin worth more than $145.
A 'Remembrance Day' red poppy $2 coin is worth more than $145 if it pops up in your change (left) while a 2016 50th anniversary of decimalisation $2 coin (right) is worth up to $10
The brightly-coloured red coin was a limited released in 2012 with just over half a million of them made and is listed on eBay for anywhere up to $500 in mint condition.
The video also points out some other commemorative $2 coins which were placed into general circulation - meaning one could easily pop up in your change - that are actually worth more.
The 2016 50th anniversary of decimal currency in Australia $2 coin had a limited run of 2.9 million which could be worth up to $10 each.
In mint uncirculated condition, these are listed for up to $165 on eBay.
A 2013 QEII Coronation $2 coin, with just under one million being made is worth up to $110 if found in your change or double that if uncirculated.
The video also points out some $2 coins made in 1988 and 1989 have a small HH on the 'tails' side but these are very common and still only worth $2.
The Australian Mint released a limited run of coins in 2016 celebrating 50 years since Australia changed to decimal currency (pictured)
A 5c piece that has been struck twice resulting in an overlapping imprint of the echidna on one side and the Queen on the other has been listed on eBay for a $55,000 price tag
A 20c piece with another standout error that resulted in the edges being shaped in a 'scalloped' pattern (pictured) was recently sold for more than $15,000
Some $2 coins were printed with HH in one corner but this does not raise the value
Another mistake or 'mule' coin is a run of 5c pieces struck in 2007 with the Queen's likeness on both sides instead of the iconic echidna.
Depending on quality these coins can fetch up to $4,000 for excellent quality, according to Sydney coin expert David Jobson from Town Hall Collectables.
He also said he had sold a 20c piece with another standout error that resulted in the edges being shaped in a 'scalloped' pattern.
In 1981 the Royal Mint in London produced the 20c coins and also the Hong Kong $2 coins - with an employee mixing up the two molds resulting in the hybrid item - he explained.
'It's very valuable. There are less than 10 that are known to exist, and they value anywhere between $15,000 and $20,000.' he said.
A similar brightly coloured red $2 coin design to the Remembrance Day version was released in 2020 commemorating Australia's firefighters.
These coins were put in general circulation but a very rare version of this coin had the red flame printed on the wrong side, over the Queen's head.
Mr Jobson said those rare coins are worth up to $6,000.
A bidding war has been sparked over the newly released coloured $2 commemorative coins honouring Australia's firefighters as some feature the colour on the wrong side (pictured)
The coin features two firefights standing back to back, with a vividly coloured fireball in the centre of the coin superimposed (pictured) - but some look different and are worth more
If you see two rings on your dollar coin it could be worth up to $4,000 in really good condition - the $1 'mule' from 2000 was accidentally stamped with the smaller head side of a 10c piece
'Very few of them exist... so depending on quality they can be worth about $6,000,' he told The Morning Show.
He urged residents to keep a close eye on the detail of all their coins as they could end up being very valuable.
A tiny 5c piece from 2007 accidentally made with the Queen's head on both sides was also recently sold for $3,000.
Many of these rare coins are created when they get clipped during the minting process, when the discs are not ejected properly along the conveyor belt during the manufacturing process.
Double-headed 5c piece from 2007 is one of the rarer minting errors (pictured). A coin in really good condition can sell for about $3500, while those in poor condition still fetch a few hundred
Facebook page Detecting Downunder said this common 'rabbit ears' fault on the $1 coin can be worth up to $30 in good condition. Many people have reported finding it in their change
The blank disc can also get double-stamped by the high-pressure die.
In 2000 a $1 coin was accidentally stamped with the head die from a 10c piece.
The coin is known as a 'mule', as it is the product of two different kinds of coin just like a mule is a product of two species as parents.
A rare 20c piece made in 1966 with a wavy baseline fault on the number 2 is now selling for up to $2000.
Although the Mint made 58.2 million 20c coins that year, only a few of them had the unique wavy baseline, making the faulty coins valuable to collectors.
This rare 20c piece made in 1966 with a wavy baseline fault on the number '2' is worth up $2000. The bottom of the '2' is usually straight
The way to spot a wavy baseline fault is to look at the bottom of the number 2 on the platypus side of the coin.
On a normal coin both the top and bottom edges of the bottom of the 2 are straight.
The faulty 1966 coin has a wavy top edge on the base of the 2 that is clear to see, while the bottom edge remains straight.
Many people also collect Australia's pre-decimal currency, and while copper pennies are common, other coinage from that era can be highly valuable.