Under EIS, a claim cannot be made by the company until it has been trading for at least 4 months.
The claim must be made within 2 years of the end of the tax year in which the shares were issued, or within 2 years of the end of the 4 month trading period, whichever is later.
Under SEIS, if the company has commenced trading, a claim cannot be made by the company until it has been actively trading for at least 4 months. If the company hasn’t commenced trading, it cannot make a claim until at least 70% of the SEIS funds raised in the round have been spent (in the correct way).
Under both EIS and SEIS, shareholders have 5-6 years to claim their relief after the company has done its part. To work out the deadline, take the year of the investment, fast forward to 31st January and add 5 years.
To learn more about the amount that can be invested under EIS and SEIS go here.