You can check your number by using the following website:

http://www.europa.eu.int/comm/taxation_customs/vies/en/vieshome.htm

More information about getting a VAT number

An overview of the new added numbers (the list below is out of date)

MEMBER
STATE
COUNTRY
CODE
VAT NUMBER
FORMAT
NUMBER OF
CHARACTERS
NOTES
 
AUSTRIA
MWSt
AT U23456789 9 The FIRST character will always be U
BELGIUM
BTW or TVA
BE 123456789 9  
DENMARK
Omsaetningafgift
DK 12345678 8  
FINLAND
ALV
FI 12345678 8  
FRANCE
TVA
FR 12345678901 or
X2345678901 or
1X345678901 or
XX345678901
11 May include alphabetical characters - any
except for I or Q
FIRST or SECOND or
FIRST & SECOND
GERMANY
Umsatzsteur
DE 123456789 9 Must be the 9 digit 'Umsatzsteur Identifikationnummer'
GREECE
FPA
EL 012345678 9 Prefix any eight digit numbers with ZERO
IRELAND
CBL
IE 1234567X or
1X34567X
8 Includes one or two alphabetical characters: LAST or SECOND & LAST
ITALY
IVA
IT 12345678901 11  
LUXEMBOURG
TVA
LU 12345678 8  
NETHERLANDS
OB or BTW
NL 123456789B12 12 The tenth digit is always B
PORTUGAL
IVA
PT 123456789 9  
SPAIN
IVA
ES X23456789 or
12345678X or
X2345678X
9 Includes one or two alphabetical characters: FIRST or LAST or
FIRST & LAST
SWEDEN
MOMS
SE 123456789001 12 Final two digits are always 01