HMRC released a list of the strangest expenses claims it received from customers trying to claim back on their 2014-15 self-assessment returns.
The expenses claims, which were rejected, include a painter and decorator claiming for Armani jeans as protective clothing, a claim for underwear for personal use, luxury watches as gifts for staff from a company with no employees and international flights for dental treatment ahead of business meetings.
Another unsuccessful claim was made for pet food for a Shih Tzu "guard dog".
Claims which were also rejected included those for betting slips, Friday night "bonding sessions" costing thousands of pounds and holiday flights to the Caribbean.
The deadline for sending 2015-16 self-assessment tax returns online to HMRC, and paying any tax owed, is January 31.
Penalties for late tax returns include an initial £100 fixed penalty, which applies even if there is no tax to pay, or if the tax due is paid on time.
Ruth Owen, HMRC director general of customer services, said: "Year after year we receive a number of ludicrous expense claims, ranging from international holiday flights to expensive designer clothing, which we would never uphold.
"Why should the honest taxpayer pick up the bill for others? HMRC will only accept those claims which are genuine, such as legitimate travel expenses or the cost of tools for the job."
Here is HMRC's list of the most outlandish claims on 2014-15 self-assessment returns:
1. Holiday flights to the Caribbean
2. Luxury watches as Christmas gifts for staff - from a company with no employees
3. International flights for dental treatment ahead of business meetings
4. Pet food for a Shih Tzu "guard dog"
5. Armani jeans as protective clothing for painter and decorator
6. Cost of regular Friday night "bonding sessions" - running into thousands of pounds.
7. Underwear - for personal use
8. A garden shed for private use - plus the costs of the space it takes up in the garden
9. Betting slips
10. Caravan rental for the Easter weekend.