There are a number of things to take into account;
Where do you live? (poor, innerr city borough, or leafy suburban council) - this
may have a bearing on the efficiency of the Council Tax department.
Does your Local Authority have a connection to your housing or is it privately rented?
Do you all (the occupiers) have individual contracts or do you rent the house as a whole and 'divvy up' the rent, or is it a House in Multiple Occupancy (HMO)?
Are all the others still
bona fide students?
Did you take time out and travel when you finished your studies? (
A. - Yes, you did)
My suggestion, since you are concerned about the situation, is to write to them and say that;
"as of ....<date> (make it a week or two previous to the date of writing)....
I have commenced full-time employment, and, as such, am eligible to pay Council tax. However, as the sole person liable.. (ie. the others are exempt)
... I am entitled to the Single (Liable) Occupant Discount of 25%....
Most Councils will be amazed about receiving a request to pay that they will not question it further than the date you state (
and is it not unreasonable starting a new job in the new year?), and if they do, you went travelling for six months, didn't you?
Here's my LA's FAQ page
Besides, aswell as joining the tax-paying masses, you can now moan at you house-mates when they surface at midday to watch Neighbours and Going For Gold (
whoops! showing my age!) - about how you support them with your taxes!!
Best of luck.