Question: “Is there a grace period on the 2.5 year test?”
Tank Guru: Yes there is a grace period of 90 days before or after the test due-date for the 2.5-year periodic test. For instance, if the last 5-year hydro test was performed in Jun-2008 and the 2.5-year test should have been performed in Dec-2010, you still have until Mar-2011 to carry out the periodic test. This does not change the next test due-date, which will still be Jun-2013 (5 years after the last hydro test). If the 2.5-year test is not carried out by Mar-2011, then you would have to perform a full 5-year test to get the tank back into compliance. Thanks for a great question.
Tank Guru blog 
Please confirm under which code/ clause it is applicable. As we need to quote.
Perhaps you have already received the information but just in case, you can refer to the International Maritime Dangerous Goods Code (IMDG) Chapter 6.7 and see paragraph 6.7.2.19.6 : “..a portable tank filled prior to the date of expiry of the last periodic inspection and test may be transported for a period not to exceed three months beyond the date of expiry of the
last periodic inspection and test…”
Please reference the IMDG Code for additional information regarding this exemption.
Could you please inform and give me document reference as your explanation above regarding grace period of 2.5 years & 5 years periodic test of ISO Portable Tank (IMO 1/T11)? I really need it to support my job. Thanks